You read that and think they're going to tunnel into your network and break your speakers? To me this is clearly lawyer CYA language to ensure that when Spotify changes their API and Sonos only supports it in a future software update, you will have been warned.
And they might. Which would be more frustrating to a user - their Sonos turning into regular speakers, or arbitrarily and randomly not functioning as expected?
Imagine the difference between your phone suddenly bricking itself, or random refusing to dial certain numbers.
That's a good point, there must be a way to block access from these devices to the Sonos mothership. I have seen zero software improvement in the few years I owned my Sonos set, so I can't say that I would miss much.