The ghost-PR problem is real though. Someone opens a PR that changes behavior they needed, you as the maintainer have to decide between three bad options: merge

The ghost-PR problem is real though. Someone opens a PR that changes behavior they needed, you as the maintainer have to decide between three bad options: merge and own the new surface, reject and feel like a jerk, or let it sit and drain everyone's time. Forking is the clean answer when your needs diverge enough. The cost is duplicate work when the upstream fixes something you fixed six months ago in your branch.