> And the amount of actual data needed to store issues is peanuts anyway.

It’s not. Take something like github.com/Homebrew/homebrew-core. There are 15k closed PRs there. There have been 20 new ones today. It’s not rare to have 10-20 comments per PRs; some of them even go over 200. Add CI status, actual PR contents (git patches), comments reactions, edits, labels, milestones, assignees, reviews, projects.

IMHO having a tool to fetch issues locally is a good idea; storing them in the repo is not.