I do think there's something to that idea - physical injury and pain is a very universal and visible experience, whereas mental illness is difficult to parse for those who've never experienced it. I also think there's some sense in which 'treatment' and 'cure' are treated differently for mental and physical illness.
A doctor wouldn't just prescribe painkillers for a broken arm and call it a day because your symptoms have been dealt with; they'd want to actually fix the problem. Depression, on the other hand, doctors seem perfectly fine with merely mitigating the symptoms. Perhaps because that's all they're confident they can do?
That would be useful.
I suppose their calibration might be cause for concern. You're with yourself all the time, so you've been witness to your own highs and lows, but others might only see your highs (for example, if you only leave your house when you're above 50%, their scale would bottom out at 50%).
I haven't thought much about how treatment fits in here. I've certainly felt both dimensions mentioned get better/reduced through treatment (having to solve less puzzles, having to solve puzzles for coarser/less granular actions).
Ultimately, 'curing' depression would be the equivalent of removing the app from your brain.
I'm really happy to hear that this helped! Remember, all models are wrong, but some are useful. This model is useful for me; use it as long as it is useful to you.