This would almost certainly be it. Calling someone to record them and using their voice later to impersonate them was done even before deep-fake voices were a c

This would almost certainly be it. Calling someone to record them and using their voice later to impersonate them was done even before deep-fake voices were a concept. With the tools available now, even a short call + the grainy connection of a phone voice line would be more than enough to make a simulated voice work.