Did Bun mass-close issues that predated the rewrite? It doesn't look like they did, as the oldest open issue is from 2021 and there are many from 2022, but maybe they did something that killed most of the old issues.
Their (public) project management is horrible, you can find fixed issues unclosed and unfixed issues closed. Not really surprising when that part of the work is completely taken over by LLM agents though.