Vlad I've noticed this before, but it's never prevented me from accessing a site like @tanner, I've just noticed that some sites I use to do UA lookups and so forth have reported that I'm using an old version of Safari.
For example, if I go to https://www.whatsmyua.info, I get the following results:
Orion Version 0.99.119-beta (WebKit 615.1.1):
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.1 Safari/605.1.15
Safari Version 15.6.1 (176188.8.131.52.16):
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.6.1 Safari/605.1.15
So it seems like the "Version/15.1" vs "Version/15.6.1" is where the difference lies, as both report Safari/605.1.15 at the end.