If anything, these are exactly the techniques that "New Math" was supposed to teach. Your brain doesn't work math the same way as a computer. People who are good at math tend to break the whole thing down into simple pieces like this. New Math was developed by studying what they did and then teaching that to everyone.

I tend to add 9 to things by bumping the tens digit up by one (7 becomes 17) and then subtracting 1 (17 becomes 16).

Most of the arguments against New Math tended to prove the point; our mathematical education was in dire need of fixing.