Person A taking a code base private that solves 95% of their problem and refusing to release fixes-and-features upstream hurts the entire community.
that person would not have even made the changes to GPL code.
I won't work on ANYTHING GPL or AGPL because I don't want to be forced into doing anything.
so how does that hurt the community? you're claiming ownership over code I haven't even written, now?
Three words: Embrace, Extend, Extinguish.
Part of what?
You've asked how does person not contributing changes upstream hurt the community. I gave an example of a real-world scenario which has happened with permissive software many times. How is it a strawman?