The app has to say "trying Stereo HD" to record in stereo, and the background of the rectangle will change to solid blue. If it just says "try Stereo HD", it's meant as an encouragement to tap on it to enable that mode.

Clearly, if this is confusing, that's of course our fault, and we'll work on improving the UX to avoid this misunderstanding. I'd just be interested - did I describe the misunderstanding correctly?