As pointed out by @lutoma (thanks!) it seems like they removed the code that auto-generates these reports, and instead instance administrators have to generate them manually (as per the kinda hidden, collapsed conversation in https://github.com/mastodon/mastodon/pull/28693/files#r1450641772)
I’ll leave the issue open as a documentation request, as there is no information on any of this unless you watch the PRs and read the source code, and also as a request to make the feature more flexible (or at least remove the cringe.)