I have Sonos speakers everywhere, so this is another interesting discovery. At least with Spotify, Pandora, YouTube Music and TuneIn Radio, I can issue Google Assistant voice requests for music, playing to a default speaker (or request a different one, on-the-fly.)
This functionality is part of the stock device, no unlock required. And it still works even when you're in a 3rd party launcher, and not the original Home screen. These settings are in the Google Home app in iOS or Android, and not on the Lenovo smart clock itself:
I wasn't able to do the same with Apple Music or SiriusXM though, I got an error when I tried, saying they weren't "currently supported." Voice requests did work for those, but were only able to play to the built-in speaker.