I remember receiving push notifications from Reddit on macOS Safari quite some time ago. Is this maybe another push mechanism?
On second thought maybe the notifications weren’t push per se and it was just using the regular notification API with some web socket or long polling in the background.
I believe this is for iOS/iPadOS
The website says it is for macOS--"Web Push is coming to Safari 16 on macOS Ventura"--and that we should look forward to it on iOS in 2023.