I wonder how they’d enforce that exactly since none of those companies are likely to have a contract with Unity that says they’d pay anything like that. Their distribution contracts are with the studios… and the studios, if they keep their subscriptions would be the ones contracted with Unity. Good luck telling MS or Sony that your little indie company bound them into a contract with your engine vendor.
On the flip side, don’t do inventory management in action games! Looking at you Horizon Zero Dawn!