True, a PWA wouldn’t have been able to get the unique device ID, which is (I think) the only technical effect of the App Tracking Transparency toggle added last year. But that toggle also has legal effects that go further [1]. For instance, apps can’t “[display] targeted advertisements in your app based on user data collected from apps and websites owned by other companies”, even that data was correlated with your app session based on, say, account name or email address rather than device IDs. But the only reason Apple is in a position to impose this kind of requirement is that they’re a gatekeeper for iOS apps. With web apps, short of government action, the best you can do ask nicely, and we all know how the Do Not Track header ended up.

[1] https://developer.apple.com/app-store/user-privacy-and-data-..., “Asking Permission to Track”