So am I understanding correctly that there was a private repo that had original code, and in that private repo, someone added the MIT licence? Which didn't make the code open source, because that licence hadn't actually been given to anyone*?

And then Roman made the repo public, effectively distributing the licence to people and thus making it open source, without coordinating with the other contributors?

I don't see any replies by Alexandr, but it feels like this could have easily been resolved with a less antagonistic response by Roman - but of course, I don't know what other history they have.

* I guess technically, it was given to the other contributors with access to the private repo - i.e. Roman did have the legal right to distribute it further under the MIT licence. Presumably, the original contributor (Alexandr) just applied that licence by mistake.