There are some IVRs where all the voice responses are prerecorded, but tbere's a person in another country listening to you and pushing buttons to pick which message to play.
I've also received those - and gotten the person pressing buttons to break script and actually come on the mic to tell me to fuck myself - but this was different, and pre-dated easy-and-cheap AI voice generation.
Callers already had the idea before, all that changed is that the joke/flight-of-fancy became plausible.