I'm also against this. Inactivity for a week or two is not enough reason to allow a known regression to be present in a release.
I should clarify that maybe I haven't processed the full context for this specific issue though. I do think it's acceptable to time out on an issue where a release blocker is claimed to exist if e.g. we can't reproduce the problem, or if it's a request for an above-and-beyond compatibility thing (like "please restore this private API, its removal breaks our application"). As a courtesy we might block a release for a small amount of time while waiting for a reproducer or a short-term private-API compatibility shim but the onus there is really on the reporter.
From what I can see though, this one is a pretty straightforward case of us just introducing a bug into a perfectly valid configuration though, just not one we happen to have in our test matrix right now.