Marketers built a profile of the buyer they want to target in their minds - a glorified stereotype. The buyers themselves didn't identify with the label.
But the marketers then demanded products tailored to this stereotype. And of course, many authors caught on, and were willing to move towards the marketers caricature of what they had in common, in order to get access.
So there's no co-option here. People are just fighting over a marketer-created niche. The niche is a bad fit to reality (in more ways than the audience hardly being young adults) but it's got enough money behind it that it's not easy to challenge it.
That being said, I don't see much connection between the G/PG blockbuster related adult readers and the coming-of-age book auditors.
Autor also conflates conservative anti-lgbt movement with pretty much anyone who reads youth adult literature which makes even less sense. The calls to remove books with lgbt content from libraries are purely political and have zero to do with what books are read by adults.
And you do not see how logical conclusion from that is that author simply dislikes YA literature? And adults too, since there is so much disgust about them, gasp, existing and enjoying entertainment.
Author literally claims it is predatory for an adult to read YA books.
Yes, when you make up negative claims about groups, purely out of nowhere, with zero argument or evidence they are true, then it is reasonable to assume you simply do not like them. Otherwise you would give them basic respect and checked up some date before making stuff up.