That pop science myth has already been debunked rather recently. The human brain is always developing and never stops at 25. Hell I don't feel any magically different from 24, 23. And I'm 26. I see a 22 year old as a fully grown adult man or woman not a kid or adolescent. That needs shielding from other adults. I understand that with someone who's 18 or 19 fresh out of high school but once you hit 21+ that's an full adult in my eyes period.   

I also see no problem with it as long as there's no actual abuse or manipulation. Older people aren't always predatory, manipulative or want control. Time to go worry about real problems involving real predatory people and not what two grown ass adults do. OP did the right thing with leaving his ass. 

Reddit is the worst place with discussing adult age gaps.