If Safari was an app it wouldn’t matter what OS version you were on. Edge will run on windows 7, 8, 10, and 11 all from the same installer.
Apple is more aggressive about removing backwards compatibility, but that doesn’t mean it’s linked to the OS.
Whether this is "coupling to the OS" or "deprecation" or "aggressive removing backwards compatibility" is really a matter of semantics.
I will say this though, it seems Apple is changing their policies since Safari v16 is now available down to Big Sur.
If Safari was an app it wouldn’t matter what OS version you were on. Edge will run on windows 7, 8, 10, and 11 all from the same installer.