I agree that it would be a better system for phones. I'm not sure about full size keyboards. Muscle memory will allow you to learn the password with only simple

I agree that it would be a better system for phones. I'm not sure about full size keyboards. Muscle memory will allow you to learn the password with only simple characters more quickly but eventually both will be learned. Then the only factor that matters is how accurately the user can type. I don't think muscle memory could ever get 100% accuracy for typing one character correctly. Anything less than 100% and longer passwords will be worse. If you type a key correctly 99.9% of the time then you will lose about twice as much of your time to wrong password entries with an 11 vs 20 char password.