The process of getting apps onto Play, is to create an Android app... so I'm not clear on what you mean. Someone will create the tooling that will automatically create this.
Trusted Web activity is just a general way to launch you PWA fullscreen from an Android actitivy.
How does that jive with the fact that Play also has books and movies? Those are not Android apps. There is absolutely no technical reason that Play couldn't also serve as a discovery and installation (i.e. icon on the desktop) mechanism for PWA-compliant applications. Users would never know the difference.
Trusted Web activity is just a general way to launch you PWA fullscreen from an Android actitivy.