Local storage is persistent when you add a page / app to the home screen (ie take the step to install and enable it as an “app”) and only gets cleared after a while when the site is browsed as a website in Safari.
This, as a user and as a reasonable developer, seems exactly right. The “progressive” part happens when I want it to and initiated by me, so the developer can’t shove it down my throat or trick me into enabling their “app”.
So much of this argument is down to entitled web devs and companies that want to take advantage of the fact I’m reading their website to start installing software, sending notifications, reading from sensors etc. without permission.
It's reasonable to think there should be some user controllable "install" process to enable this.
But it's also reasonable that an application should have permanent local storage in some cases.