I have an Arc, a Sub, and two Play:3's as surrounds. I noticed that when asking Google Assistant on the Arc to play a song (from YouTube Music, in this case), its response cuts off the first few seconds of the song. However, when asking the assistant to play a song on a Google device, such as Google Nest Mini, it finishes its response and the song plays afterward without the beginning being cut off.
Just in case anyone else may have experienced this scenario also, I spoke with a senior Sonos engineer last week who said he would submit this as a feature request, so maybe a future update will address this.
Ultimately, this is nothing more than a very minor inconvenience, but it would be nice to be able to hear a song in its entirety without interruption when requesting it through Google Assistant.