Not sure there’s any deepfakery on the Michael Caine audio. Peter Serafinowicz (the other collaborator and originator of ‘sassy Trump’) is well known for his Michael Caine impersonation.
Most likely not, and the parent comment seems to agree with you on that. I think they were just trying to point out, in general, that the arrival of commonplace audio deepfakes might be way more disruptive than video deepfakes, despite a lot of people (including myself) who used to counter-intuitively think that video deepfakes would be more disruptive.