> For example, on https://github.com/gap-system/gap/pulls it says "Pull requests 78" in the "tab list", but the PR list view reports "35 open" (the number 78 is correct, and confirmed by e.g. `gh pr list`)

Surely a scaling hack where they use "estimation" queries that return "kind of right" results instead of 100% correct data, as it's less load on the infrastructure. Not necessarily a bug as much a shit choice from product perspective.

If the numbers were all that is wrong, that'd be OK. But it fails to list all data -- so the only way to navigate to the missing PRs is to know their number, and manually inserting the right URL (or to go to another PR, and then edit the URL in the navigation).

Sorry, but I don't think there is any way this can be classified as "not actually a bug"