From the author’s blog post, which goes into more technical details:
“While there’s nothing I could do about this from the iOS device itself, as it turns out the same underlying iTunes (WiFi) sync infrastructure I’m using allows you to also install and remove provisioning profiles from devices (since Xcode also requires this ability to manage profiles for developers). Before installing an app, I remove all the existing profiles on the device to make it look to the system like there are no other apps installed, and then once the app is installed I reinstall all the profiles. It’s very simple, but it works.”
I saw that line, but I must be missing something, or the article is. When I install apps with my free apple ID, they all use the same provisioning profile: I can see as much in Settings. However, I can't install more than three apps this way.
“While there’s nothing I could do about this from the iOS device itself, as it turns out the same underlying iTunes (WiFi) sync infrastructure I’m using allows you to also install and remove provisioning profiles from devices (since Xcode also requires this ability to manage profiles for developers). Before installing an app, I remove all the existing profiles on the device to make it look to the system like there are no other apps installed, and then once the app is installed I reinstall all the profiles. It’s very simple, but it works.”
http://rileytestut.com/blog/2019/09/25/introducing-altstore/