>but calling the system's built-in application installation mechanism "not primary" is absurd.
So you're arguing that because play store installs and random .apk installs both goes through packageinstaller, the concept of a "primary" install method doesn't exist?
If we're using "primary" to mean "first-party" (as in your original comment), then the system's built-in package installer is the most first-party of all, so it's definitely not "not primary".
If we're using "primary" to mean something like "most popular", then I don't see how the term "sideloading" would make any sense to describe "not primary". Are we side-commenting here, and side-submitting HTTP requests, because we're not posting to Facebook, the primary website?
So you're arguing that because play store installs and random .apk installs both goes through packageinstaller, the concept of a "primary" install method doesn't exist?