If they hard fork, a lot of apps that are generally "necessary for the average person" (e.g. Uber, banking apps, Gmail, Whatsapp/Wechat/Line) might stop working.
I'd like to see them lay more ground work for web apps but it's a tough spot and the easiest choice at the moment is to continue with AOSP.
Until that changes, webapps aren't going to sell.
Even Google tried multiple things to "sell" the idea of webapps (e.g. Polymer project) in 2011-2015 and failed.
Funny enough, Wechat kinda succeeded at webapps in China because there's a strong user preference to stay inside one monolithic "everything app".
Of course there is. Sent from my daily driver Librem 5.
Disclaimer: It is less secure than GrapheneOS, according to the GrapheneOS threat model.
Above that, not much would change for a few years anyway, because apps still target ancient Android versions.