No that is NOT my opinion, I just want to highlight the logic flaw I see here. You cannot say that the same thing (underrepresentation) is a problem in one case and not in the other, that's just .. weird.
There's no path for promotion beyond "developer" without becoming a manager, but then you're not doing the work you're great at, so there's a disincentive to promote you, but the developers want to have career growth, so they get restless and eventually leave the company for a different one, usually getting a salary boost but possibly still being stuck as a 'developer' because they saw no advancement at their previous company.
I'm struggling through a similar situation now, although I have project management and team lead experience, I was never officially promoted because they were small companies and didn't want to bump my salary (or believed they had a flat heirarchy and "titles were meaningless").