It’s relatively ‘easy’ to change the stereo pair from a ‘music room’ to ‘surround speakers each time you want to alter their function, ultimately it’s a bunch of keypresses, and around probably two or three minutes of your time. Additionally, each time you do so, any TruePlay settings will be erased. My bet would be that you quickly find that it’s just too much effort. Sonos has never made it a ‘quick switch’. The cynical voice in my head suggests it’s due to the impact it would have on sales, but there is also the fact that there is a lot of change in the nature of the way the connection changes in the system that makes it more understandable, surrounds are essentially ‘slaves’ of the surround bar, where as ‘normal room’ speakers are ‘masters’ of their connection. And the ‘type’ of data and the flow is substantially different. 

In this functionality, there is no difference between S1 or S2. 

@Airgetlam , thanks, I guessed as much.  As I haven't set up the surrounds yet I suppose I will wait and see if their addition warrants keeping them permanently in that room. I already have a hifi there with a zp90 so am a bit loathe to clutter it with more gadgets permanently.