I've wondered about this with Sadie. She doesn't hover. She will sit regularly (on her butt) only when concentrating on something (birds outside, for example). If I ask her to sit or she sits on her own, she sits to the side, more on her hip than on her butt, with both legs out one way.
Riley sits like Sadie sometimes and on his butt more often. He'd really rather just lie down, though. He's a bum.
Sadie also isn't bit on laying down sometimes, but she'll definitely do it, especially b/c she sees Riley do it and get a treat (if I ask him to do it). She doesn't like to sit on tile, but I think that's a traction thing. She'll sit on sidewalks or on dirt or whatever is outside.