A large, complex, unasked for PR is pretty likely pointless to throw at any serious project. (Well, it's pointless if your goal is to merge something.)
Working together is a two-way process. To land a big change, the bun people probably needed to have been working/coordinating with the zig people throughout. E.g., zig outright cannot accept PRs that break the language in unplanned ways and any conflicts with the roadmap would need to be resolved.
I would assume the bun people know all this. That makes it more of a publicity stunt than a serious attempt to contribute to zig, and we should probably all treat it that way.
Of course, and it is expected that large pull requests/RFCs are iterated on. I will not believe Bun seriously asked for a pull request to be merged with absolutely no expectation of back and forth discussion. But this isn’t what happened. The whole reason everyone thought it was rejected by Zig because Bun used LLM to generate it was because they responded in a way that someone would if they didn’t want a certain pull request accepted under any circumstances. Which is my point; it I just insane that their largest project submitted a pull request, and they just rejected it with prejudice, gave some statement saying the real and potentially fixable reasons why, then turn around and say we don’t want your help, we are doing this in house.