The purpose of a system is what it does. If the org truly cared about under-leveled employees, it would get fixed rapidly.
But they don’t.
I’ve seen enough people glossed over repeatedly and then when enough people leave and the org is in a less leveraged position, then the promos are no longer an issue. Such BS.
You have to realize that a company is always optimizing for efficiency and salaries are no different.
Giving out promotions when people are already working at the level they'd be promoted to is simply a waste of money.
This is the author's biggest mistake. If you voluntarily work on tasks above your pay grade you are signaling to the company that you don't need a promotion.