The current reason why build files are committed is because of legacy / browser support. That is, the browser build is committed to the root dist folder, which can be used as-is in browsers.
The reason why there are TWO dist folders, and it's copied to both is because of the monorepo setup. When it was moved to the appropriate package folder, it broke documented links for CDNs which convert a Github repo's file structure into URLs.
Similarly, because of these CDN links, the root package.json has a version number, even though many monorepos do not version the root package.json.
It's possible that this setup is no longer necessary. Ideally, build files would no longer be committed (but would be published), but some research would be needed (with information / evidence here) to say if that's safe to change / remove.