It's somewhat common on Duolingo to see sentences like this. As I understand it, it's entirely intentional. They're designed grammatically correct nonsense.
It forces people to think about and understand the individual words and grammar, without being able to rely on sentence context clues to guess words and answers.
That totally makes sense! Universities are NOT young men. Why? – Even though Classical Latin is our subject in Duolingo, we should consider that the concept of a university, in a modern sense, was not present during the Classical Latin period and Roman paganism. Our modern universitas first appeared in Bologna A.D. 1158, when the academic freedom was manifested in the Constitutio Habita; or, in any case, the direct ancestors of the university were not around before the foundation of medieval Islamic madrasas (such as University of Al-Karouine, A.D. 859, the oldest university still existing); so, there was from the very beginning no personification of the concept of Universitas happening – and in case there was, the deity of Universitas was just seen as an allegory. – If we personify the concept (let us say, in the archaic/classical meaning of the word ”universitas”: a number of persons associated into one body, a society, company, community, guild, corporation, etc), we’ll soon realise that “universitas” is a feminine word, thus regarding a goddess.
I can imagine a scenario where young students are protesting for this or that reason, with statements such as "Universities are founded on young men!"
And then an opposing man says: "Universities are not young men! They are walls and bricks and books and old masters of arts!"
I'd say that sentences like these are helpful to the learning process. You are eventually going to come across real sentences that you find confusing and you will need to rely only on your knowledge of the morphology and grammar to parse the meaning. Sentences like the example here are merely forcing the confusing meaning.
It would certainly be detrimental if every sentence we learned was a nonsense sentence, but it's helpful now and then.
What's wrong with "ich renne in die Universität"? The informality of the sentence coupled with the long form "Universität" rather than the more informal "Uni" is slightly weird, but it's really not bad.
Probably you believe that the sentence means "I run into the university" in the sense of running face first into a brick wall, but that's not what the German means. It means you run to the university and you continue running when you're inside the building until you get to your classroom, or to wherever you wanted to go.
I don't believe that in die Universität rennen would imply running into a brick wall (because I am a native speaker of German :)), but I believe that the English sentence does imply that (and that the German sentence would naturally have "zur Universität", and if I really wanted to stress that I don't stop running until I reach my destination, I'd probably say "renne zur Uni und bis in den Hörsaal" etc.).
But that is just it: To my mind, sentences are bad when they are unintuitive. This has nothing to do with them being fun or wacky (or, to some people's minds, silly or plain useless). I'm totally fine with saying that my young owl is reading books (even though ordering a coffee or asking for an ensuite room with a double bed might be more practical, it's also not very exciting... :)). What I have a problem with are sentences that sound stilted, where the prepositions are just "off", that only work in one of the two languages, or where I can't construe a context (which I usually find very simple with the "talking animals" sentences -- pretty much usual fairy tale fare :)). The "run into university" sentence is a combined case of odd preposition/doesn't translate well/can't come up with context, while this one here is just plain weird and without an obvious context (more along the lines of tsuj's Arabic sentences above).
Sorry for the longish rant. :) My point is that I feel that "illogical" sentences are confusing and break my flow while learning, while unnatural sentences (e.g. odd use of prepositions or unexpected collocations like "ich benutze einen Hut") don't help me to develop a feeling for my target language.
I just came across the sentence "A tail is not a horn" in the Dutch course (in the very beginning of the tree; the lesson is "Animals", and the negative pronoun geen/"not a" had been taught two lessons previously).
Now, this is a sentence that I presume is supposed to teach very much the same structure as this one, but because the two things being compared come from the same category (i.e. animal body parts), I find it a lot more intuitive. And it doesn't just seem to be me: There is hardly any discussion following that particular exercise, just a few people asking for clarification on the use of geen, but nothing about the semantics: https://forum.duolingo.com/comment/9489398
Maybe it has to do with the similar but different ordered phonetics between "iuvenes" and "universitates". Like in school the sentence designer struggled to learn to spell "iuvenes" and kept spelling it something like "iunevers" and their teacher said to them, "Universities are not young men!"
I think there is quite a difference between whimsical, silly sentences ("my goat drinks beer"), which I personally find quite fun (although I know that they annoy some people who'd rather learn "something useful"), and ones that baffle the reader. If this sentence contrasted two things that were more in the same category (say "schools are not universities" or "youths are not old people"), it would be a lot easier to understand. Such as it is, it certainly works to show off the predicate nominative -- no problem with that. But without a context -and the reader quite likely still trying to get to grips with basic vocab-, the immediate effect is "huh, did I miss something? I'm sure this has another meaning I'm not getting right now".
The only sense behind this sentence for me might be to teach/remind native American speakers that "u" in other languages is not pronounced as "iu" as they tend to do automatically. So these two words maybe show the difference when it's right to say "iu" and when not. The more "normal" sense this sentence would contain, the less it would be obvious whats the point of attention because nobody would make up his mind about it.
Unfortunately, some spoken sentences in the Latin course are pronounced quite poorly because some of the American voices don't really get the "u" and "r" as they are ment to be.
Non anglophonic native speakers should be used to differ between "u" and "iu" anyway and especially Italian, also Spanish or at least Austrian or Bavarian native speakers should have no problems with the rrrrolling "r". :D