The choice with animal sentences is pretty much either boring or anthropomorphic. Most of the languages have animals forever drinking water or milk or eating something, mostly bread. But the Spanish course does have horses dancing in boots, elephants riding bikes and sheep working in stores. Personally, I appreciate a break from boring.
You better get used to that. Since animal names are just one portion of the core vocabulary that Duo has to drill, they routinely have animals doing human activities to drill different words. In the Spanish course they get much more creative. They have horses dancing in boots, elephants riding bikes and sheep working in stores. It actually does cement your knowledge better to construct unusual sentences, because you have to use your grammar skills, you won't have any sense of having heard the sentence before and knowing what it is without understanding why.
Duo likes to personify animals in their exercises. It happens in all the courses. In the Spanish course we have horses dancing in boots, elephants riding bikes, and sheep working in stores. These sentences are simply a way for you to practice vocabulary and grammar without relying on familiar sentences you may have heard. It's also probably more fun to make up these sentences for Duo staff. But in your native language you can create any sentence about anything at all, whether you have ever heard it said before or not. Getting away from the more familiar sentences is actually a better way to test your understanding of the grammar and vocabulary. Duo isn't a phrase book. They do cover many common phrases, especially the idiomatic ones, but the sentences are not necessarily designed to reflect common Dutch sentences. In some cases the grammar points that they want to make would be better made using a more complex sentence then they want to deal with. So some sentences can be a little "off", although not incorrect. But that tends to happen more with non Germanic languages.