I don't see how patents on trivial stuff like synchronized playback are supposed to help startups. The big corporations are sitting on enormous piles of those which makes entering their markets extremely risky.
It might not be trivial to achieve technically, but at the point you have multiple speakers dotted around a multi-room space, making them all play the same thing in sync is a fairly obvious idea, which I think is more what is being argued here.
Depends how broadly it’s claimed. A detailed claim that gets into the technical specifics of how this is implemented might well be nonobvious. A broad claim that covers all possible ways of synchronizing audio is a tougher sell.
But the patents are often not on the technical implementation nitty-gritty, but on the very general idea of "Two speakers that play the same song in sync".
The latter ("concept patents") just stifle innovation.