The objection is the tiniest bug-fix windows get everything but the kitchen sink.
These are both uncomfortable positions to occupy, without doubt.
And the whole reason for a filesystem's existence is to store and maintain your data, so if that is what the patch if for, yes, it should be under consideration as a hotfix.
There's also the broader context: it's a major problem for stabilization if we can't properly support the people using it so they can keep testing.
More context: the kernel as a whole is based on fixed time tables and code review, which it needs because QA (especially automated testing) is extremely spotty. bcachefs's QA, both automated testing and community testing, is extremely good, and we've had bugfix patchsets either held up or turn into flamewars because of this mismatch entirely too many times.
It's a bcachefs thread, and I'm the resident bcachefs expert, so.... :)
I'm not terribly invested in these threads, the actual decisionmaking happens elsewhere. But they are a good opportunity to educate people on the whole process of shipping a filesystem, talk about what we're doing, what our priorities are, all that jazz.