Subs are based on user sales. So Genshin installs 20 mil copies but only 5000 whales pay for it (ignore these Numbers, just an example), Unity would get paid for 5K sales but not for the other millions of users.
That's why they want to change to charge per install.
?
How many paying users there are doesn't matter. If Genshin had 20 million users spending 100 dollars each, or 5000 whales spending 400,000 dollars each, Hoyoverse would owe Unity the same amount of money.
The subs are based on the company's finances, not how many sales or something.
Unity wants to add the runtime fee because they want more money. That's it really.