They knew about it in advance. They decided people shouldn't care about that data.

https://github.com/neovim/neovim/pull/13973#issuecomment-789...

But they hold themselves out as being a normal software project, suitable for use by casual users. They even talk about having a "stable release" and advertise various sponsors.

If it's really just a toy with no expectation of not unexpectedly destroying user data then they ought to make that more clear.