If you don’t want people to fork, just go propietary or don’t release it as GPL.
Metro app, which is a fork without propietary Google code and completely offline, now suggets the user to install Retro Music Player from Play Store because Retro’s developer has maliciously implemented a “plagiarism” check in the code.
To play devil’s advocate: I wouldn’t be surprised if this was just a jab at people who take apps, fill them to the brim with ads/trackers, republish them on Play Store, and then don’t publish source code even when requested.
Not necessarily for people who actually fork/respect the license, especially given that it is just a package name check which would have to be changed to publish on Play to prevent namespace conflict.