On Chwyto! you can strengthen two or three finger grips without cheating

By using holes for this, we cheat by using the friction of the side walls. We rub the sides of our fingers in the corner.
Practicing twos on flat grips means that you have nowhere to hide with your weaknesses. You can also better follow the progress from training to training, because the element of randomness in the form of more or less squeezed fingers (like in a regular hangboard) will go away.