Actually, back in the 1980s I recall that simply penetrating past the sphincter was considered a full penetration anal fuck even if you were a quarter way inside.
Same here. I love eating and fucking pussy but the ass is a super-private, super-intimate part of the body that comes with the 'poo taboo.' I prefer female ass, especially for extended rimming sessions and overall because the smell is slightly less harsh than most male anuses. Different but similar.