I was able to reproduce functioning voice dictation with the 29.4 build from https://emacsformacosx.com/builds
Installing from https://emacsformacosx.com/emacs-builds/Emacs-29.4-universal.dmg
Got it. I see it does work for me. (I stopped using that distro last year because it's slow and buggy in other ways.). That's perfect as I can try to analyze it now. I'm curious, perhaps morbidly so.
Thank you for that. I also verified that his 30.1 build does not take dictation, should it be a difference in compilation by the distro producers.
I'll dig this afternoon for a bit.