Ok I see what you mean and I agree ! Kinda talking out loud so you can skip it but in a past version I just gave extra mana when playing the Tetris part like you should (like you're doing) but it didn't feel good so I scrapped it and didn't touch it again. I think I had a solution floating around in my head but I'll have to test it, I imagine something similar to "Limit Breaks" or Dicey Dungeon's "Supers" but usable only if you made a 4 lines combo. What I mean by that is character specific enablers.
Anyway ramblings asides I truly thank you for your time and useful feedback !!!
I've played Peglin a little bit, it's definitely an interesting concept. Thanks for the suggestion !
Haha glad to be the reason you wrote so much about Tetris !