As someone with an education background, it’s not always a bad idea to turn a not-excellent student into a tutor. The ideal candidate in this situation would be a student who understands the content but who might be unmotivated or skeptical of why things are done the way that they are. By teaching a younger student, he or she gets a glimpse of things from the other side, which can build confidence and demonstrate the usefulness of the lessons they were already taught.
Note that this isn’t always the best situation for the student being tutored. You hope that it benefits them, but the main focus is to get the older student to buy in and partner with you in a way that they previously wouldn’t.
To me, this logic perfectly fits the Anakin/Ahsoka story.
Learning to teach is helpful in certain ways, once you’ve mastered your own subject. I was often the best in my art class, and the teacher would sometimes have me teach others, but this was because I was also better than the teacher. So there was nothing they could teach me either.
Which comes back to Anakins base problem. Not having a padawan. Its the fact that he is potentially more skilled and powerful than Mace and Yoda. Something he would need to be tested at to prove. Which if he was, then yes, he would warrant the rank. Being as Obiwan can still kick his ass, despite Anakin being better Offensively, means he has more to learn and is not a Master capable on taking of Mace and Yoda.