But they seem to use 'foot' in your link only to indicate they mean ending of a leg, and both paw/hoof are 'feet' in different, broader meaning than human body part, no?
Just like moon is a class of celestial bodies, but it also has narrower meaning of one specific body.
The question was if there are places where middle finger is non-vulgar, I simply pointed out popular vulgar gesture used to be different, so, yeah...The middle finger gesture and the two finger gesture are, as far as I recall, very unrelated. The former has an agreed origin, for a start, the latter not so much.