It's been available much longer than 11.3, was this a typo for 1.1.3 when it was actually added?
https://dockyard.com/blog/2017/09/27/encouraging-pwa-install...
They do even auto-delete the PWA-apps
[Quote]
If the user doesn’t use the app for a few weeks, iOS will free up the app’s files. The icon will still be there on the home screen, and when accessed the app will be downloaded again.
Not very trustworthy for using a PWA on iOS it seems :)
I'll admit it's been little more than a fancy way to add a bookmark to your home screen with the option to hide the browser chrome, but it's been there for a long time.