So... If the Unity's secret spyware and algorithm suddenly decides to count an update as a new installation, you suddenly get slapped with a huge bill. Especially if you release multiple small patches and your whole player base is counted multiple times.
Ah yes, because it's that difficult to spoof a new PC. You can run a tool similar to a kernel level anti cheat "ban bypass", run the game, and cost the developer up to 20 cents. With a relatively simple script, this can be done many times per hour on a single PC, easily racking up cost for the developers.
This is a bad idea, no matter how you implement it. If it goes through, it will be abused.
Yeah as petty as some people are over games I can see a developer pissing them off and a bunch of players banding together to uninstall and reinstall games over and over. They could even script it. Bad idea all around.
Except that that is a back pedal on their part and their FAQ plainly says they actually have no way of tracking what is a new install versus a re-install; which is why they decided to count all installs to begin with.