The "PWA support" that people are clamoring for is the option to open a web page shortcut in a browser window without an address bar.
That's a big part of it, but PWA offers more than that!
For example it has facilities for caching the web application so that it can work offline. They can also register URL handlers on the system, which is very useful.
Programs that don't require an entire web browser to run can already do all of those things.
They can also do a lot of other things that a browser's sandbox would not allow
Until Google decides to give developers the ability to let the browser invade the rest of the system, which, in six months, will suddenly be necessary for everyone to do things like bank online and pay utility bills.