Duck Confit is accurately only done by cooking it at low temp in duck fat. Using any other liquid or oil would be poached

Not very common. I remember reading somewhere that it might be due to breeding habits being very different between the two (whitetail does run away and have to be caught, whereas mule deer don't). https://www.deeranddeerhunting.com/deer-scouting/deer-behavior/hybridization-a-unique-tail-of-whitetails-and-mule-deer

Another common one in California, Oregon, and Washington are hybrids between mule deer and blacktail deer which are fertile. More rarely, in places where both species occur, hybrids of whitetails and mule deer occur.

Ah yes, the classic hotelier-guest confidentiality privilege.