If Apple freezes Big Sur at 11.6.6, the least they can do is change the name to Big Sure. I upgraded a client to Big Sure 11.6.5 from High Sierra - long story/software limitations... and it was a nightmare waiting to happen. Look up the mdworker file issue.
Fortunately I caught that little minefield after one computer and did the work to get past that bug and got Big Sure installed on all of their computers, but it's _really_ ugly. the mdworker bug makes this permissions bug look puny.
I can't upgrade this client to Monterey on all their machines because I'm still at a software limitation, but I have upgraded a few of their machines that I can to Monterey and so far, Monterey is better in a lot of ways - fixes this opening files/permissions bug, Remote Desktop is _much_ more stable, and it is actually faster - for starts.
We are using the workaround for now, but if I can I'm leaving Big Sure far behind ASAP. The 11.6.6 update really didn't help.
I've been using Apple products and FileMaker/Claris on thousands of computers since 1987, and this is reminiscent of some of the days of System 8 and 9 - yuck.