Unity wanted to charge for every single "install", where that category was defined so broadly that even loading the game in a web browser was an "install", and someone downloading and deleting and downloading the app over and over on a device was also repeated "installs".
Here Apple is tracking an install across the entire user account per year, so even if you have tons of devices and install the app on every single one of them, that's still just one "install".
Unity kept revising it over and over again so these two got removed IIRC:
> that even loading the game in a web browser was an "install", and someone downloading and deleting and downloading the app over and over on a device was also repeated "installs".
Here Apple is tracking an install across the entire user account per year, so even if you have tons of devices and install the app on every single one of them, that's still just one "install".