I automatically assume anything before that would be vulnerable but you are right, sometimes it isn't. But Apple doesn't tell us that info any more. I liked it back when they did.Clear now that it was just a typo but it was just confusing because you wrote older than macOS 14 instead of macOS 13.
In any case, we just don't know if Monterey's Safari is vulnerable. Someone who follows WebKit development and understands the bug this fixes and where the code it fixed was introduced could determine if macOS 12's Safari/etc is vulnerable but not being patched or if macOS 12's Safari/etc wasn't vulnerable to begin with. Unfortuantely, it seems unlikely someone who could do that analysis is going to share their findings widely.
Then for that and reasons like that, I avoid Safari when running on any no-longer-patched macOS.
I use Safari almost exclusively for day to day tasks for many reasons, so I do pay attention to these issues.