I've seen a few post from 2019 & 2020 regarding TTS vs Broadcasting to Google Hub devices.
TTS appears to bring up a "Casting" app and does not resume what video/steam/music that was previously playing. I'm hoping there is a way to broadcast to select devices.
There was a post in April from @embrito that described the need well.
- Not interrupt whatever is playing (instead, pause and continue after announcement is complete).
- Play some sort of sounds effect before the announcement (like in the airports) so your brain gets "triggered" and focus on it.