Is Pâté in Bánh mì standard or not?

Yes. Also, Vietnamese patê is a bit “different”. You’ll find that it’s not easy to get the real recipe. The same can be said about Vietnamese butter (or is it “mayonaise”?).

A couple of times I brought back with me, in a Coleman cooler with some ice cubes, vacuum sealed packages of Vietnamese patê. Flying direct the patê survives 12hr flights just fine. (in the good old days before 9/11 of course)