I attended one of those training's and the strong suggestion was "use that radio shutdown trick at your own risk, not recommended." And, as I mentioned above, I've never needed it.

I understand why some installers are upset about some WiFi band "chatter" that is not necessary in a wired system. Now that the SONOS controllers are mostly EOL, SonosNet is not required. With proper management, one could carefully turn OFF some radios. Unfortunately, I stress to my customers that the powered speakers can be moved around as needed. This is painless when SonosNet is working. If some areas are blacked out, I'll start getting calls that will be difficult to manage remotely.