Well joke's on you, on macOS Safari is decoupled from the operating system.

Nope it's not. You can't get v15 or v16 even in Mojave which is just a couple of years old.

https://en.wikipedia.org/wiki/Safari_version_history

The fact Safari is no longer supported in Mojave doesn't mean you can't get Safari updates separate from OS updates.

You're arguing semantics.

The simple fact remains that Mojave doesn't have access to Safari updates.

I think you're arguing semantics. Apple's refusal to push app updates to much older OSes is unrelated to coupling Safari's release with macOS.

Safari team is constantly deploying new features and you can get advance access through Safari Technology Preview. These aren't part of the system but are standalone applications. The simple fact that you can download multiple versions of them on your Mac is the point. New versions don't ship when macOS updates ship. OP is right.

You just agreed with him by saying pushing updates to older OS versions.

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.

Exactly.

But it doesn’t run on Windows 95 so…

Apple is more aggressive about removing backwards compatibility, but that doesn’t mean it’s linked to the OS.

Safari uses frameworks from macOS and iOS which is the reason you can't get v16 in Catalina or before.

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.