This problem is created by the ISPs; When they issue fully functional rDNS entries to every IP they control.
The entire Internet should frown on this practice (for many reasons).
I’m not even sure if they are required to follow any standard that could mitigate this situation.
I mean, I do understand the need to create functional rDNS entries.
But they should be done in such a way that they can’t be misused/abused.
One simple solution is to prepend all entries with an undercore:
_198.51.100.100.rev.sfr.net
could still resolve to an IP and pass FCrDNS checks.
But such a name should never be issued a cert.