According to what Unity reps said elsewhere, they have no way of knowing what's a bought install, what's a demo, what's a charity bundle, what's a pirated install, and what is someone loading a webpage with a WebGL program integrated (every page view = 1 install).
Instead, they want to estimate how much people owe them. Using secret methods with no accountability.
Specifically, ublock origin. The "origin" part is important.