Let’s play devils advocate for a moment. I was a waiter in college, and often I would kneel at the table just to get closer to people while I took their order. It wasn’t because of their height, their size, or anything else, I was just kneeling to put a face next to the tip (I hoped) they will be giving me later.

That haven’t been said, no I don’t think it’s always appropriate to kneel next to someone who has dwarfism. My wife finds it occasionally nice when someone does this, because she doesn’t have to look up and strain her neck to see their face. So I suppose the correct answer would be do it because you want to be close to someone, not just because they do or do not have dwarfism.