I don't think these illogical/absurd/unreal sentences help you learn the words. I doubt I will form an association between "apple" and "dizzy" or that, if I did, it would help me remember one or the other next time I see them. Is this being done intentionally, i.e. is there any evidence that it helps you learn?
I think you may be right - i am learning czech on duolingo also. My mother is czech, so i often ask her about the "weird" sentences. Frequently they have a very specific political meaning or are a joke that czech people of a certain age would understand. I think the idioms or "weird" sentences reflect the humour of the person/people creating the course.
There is also the possibility that the persom creating the Hungarian content has a more literal "book" knowledge of english, and that may be causing the disconnect.
I only know one Hungarian lady - i will ask her about these dizzy apples and if she gives me any helpful info i will pass it on!
In Hungarian, you use the singular after numbers or expressions of quantity e.g. "öt alma" not "öt almák" literally translated in English "five apple" not "five apples". Similarly for expressions of quantity like "néhány", "sok" etc , the noun will be in singular format "néhány alma", literally in English "some apple". Because the noun is singular, 3rd person singular is the correct way to conjugate the verb i.e. "szédül" not "szédülnek", however obviously the English translation "Some apple are feeling dizzy" or "Some apple feel dizzy" is incorrect.
You are making good points here, have a lingot :)
Let me sum it up - 1. numeral adjectives are just like any adjectives - they don't even make the noun plural 2. In Hungarian, to this day, conjugating by syntactic amount is dominant - no matter that "öt alma" is plural semantically, you'd conjugate it by alma therefore singular. A corner case are "I and my sister" kinda sentences with multiple subjects. (In this case, I'd prefer treating it as "mi" in Hungarian as well.)