That probably works if there's anything to transcribe, although the goal of the robocallers is probably to get transferred to a human being as soon as possible

That probably works if there's anything to transcribe, although the goal of the robocallers is probably to get transferred to a human being as soon as possible (i.e. pressing 0, or just doing nothing and waiting for the call to be transferred to a human, which I see happening a lot on my own small business phone system). Unfortunately those are also behaviors that legitimate callers might exhibit. I'm guessing google is reasonably happy with how it works though