If you hesitate changing it because you worry about users using it anyway you are hurting the fraction of your users who are not using it.
Everyone is brainstorming ways to work around Zig's lack of "private". But nobody has a good answer for why Zig can't just add "private" to the language. If we agree that users shouldn't touch the private variables, why not just have the language enforce it?
Thing is, I don't have an opinion about what users should do. That's entirely up to them and the trade offs they make in their contexts. There are scenarios where you might want to access a private field.
But it's also a question about simplicity, adding private to the language makes it bigger without imo contributing anything of practical value that can't be achieved with convention.
Companies with monorepos could easily just ban the annotation. OSS projects could easily close any user complaint if the repro requires the annotation.
This seems like a great compromise to me. It would let you unambiguously mark which parts of the api are private, in a machine checkable way, which is undoubtedly better than putting it into comments. But it would offer an escape hatch for people who don’t mind voiding their warranty.
If they want to ignore the API contract then that's the right response. The maintainer chose one thing to preserve their ability to provide non-breaking updates. The user doesn't care about that, now it's on them to maintain that code which they're sinking their probes into.