Knowing that mobile devices, more often than not, has its own proprietory browser and could be an obstacle to reach the multi-browser capability should manufacturer choose to redesign their browser far from the current acceptable browser engine where PWA works best.
I see your point elycoinz and would like to add that currently, PWAs works best on Android-based browsers. It is only through this mobile device OS that some hardware feature of a device could be access with no issues (like cameras, calendars, location, etc.).
I'm pretty sure it would be a drag should the mobile device uses a non-native android browser.
I hope Yappadappadoo already have a team for this.