Thanks for catching the issue!
FWIW, I think that reverting something several months after it lands is a bit disruptive and the test case causing the revert feels arbitrary without further context that should have been explicitly mentioned in the reverting commit message. The context is that this change broke a test that should have caught the failure: https://github.com/llvm/llvm-project/blob/main/clang-tools-extra/test/clang-tidy/checkers/misc-static-assert.cpp#L86-L87 which led to this bug report: https://bugs.llvm.org/show_bug.cgi?id=50532. I'm still not convinced the correct action was to revert a change with no discussion that already was shipped in a release, however. Next time, I think it'd be a bit friendlier to mention the regression on the patch to see if the author can do a quick fix -- if no one noticed it for almost four months, it's hard to argue it's a critical issue that needs an immediate revert. (The reversion mildly worries me because this change already shipped as part of Clang 12 and larger reversions make for harder git blame logic to follow along with, both of which can lead to potential confusion for folks.)
And LLVM policy agrees with you.
Reverts should be reasonably timely. A change submitted two hours ago can be reverted without prior discussion. A change submitted two years ago should not be. Where exactly the transition point is is hard to say, but it’s probably in the handful of days in tree territory. If you are unsure, we encourage you to reply to the commit thread, give the author a bit to respond, and then proceed with the revert if the author doesn’t seem to be actively responding.