It does seem vague though. It’s almost akin to saying “I could’ve done this in half the code”. Well add your PR then.
This is a situation where tu quoque really doesn't smell like a logical fallacy. There is a lot of fuss about "being right" over "being helpful."
From my perspective, there are two reasons why someone would build an entire project instead of opening a PR:
* Merely to be able to point and it and say, "see? see? I was right!" How obnoxiously childish.
* Implementing his ideas into a mature/non-greenfields codebase wasn't in-fact "extremely simple."