The Sonos controller app does not seem to respect / respond to changes in the iOS text size. No real excuse for that these days.
Secondly, the text size of the artist and album are way, way too small on iOS iPad mini lock screen display (see attached pic). It's barely readable even with glasses on. I use this frequently just to see what's playing when I shuffle the entire library and it's not like there isn't plenty of room to make this more readable, even without increasing iOS text size.