That is true -- grouping is the feature most lacking from the built in integration in my opinion, though I can understand why the Hubitat team doesn't see something that vendor-specific as a core functionality.
To fill the gap, I run an instance of the excellent node-sonos-http-api on a RPi and use a little integration with it that I wrote for Hubitat: Control Sonos Music in 2020? - #26 by tomw