The distribution is a distribution of game licenses with associated terms, and those terms don't dictate a limit to the consumer on the number of installations on hardware they own for private/non-commercial purposes.

Right, but it's not unity who is selling the game license. Nor are they limiting the end consumers ability to download the game as many times as they wish. They are just charging the dev for the use of server space and traffic.

argument against the terms of the licenses, not the terms of their arrangements with devs.

The arrangement with the devs is literally the only thing they have control over.... it's a service based company. Services are allowed to change their terms whenever they want, you don't own access to their services, you pay to access them. If they change their terms of services and you don't agree, you stop paying for the continuation of service.

TOS agreements are for the benefit of the company, not the benefit of the consumer. You can sue or arbitrate over the TOS, but it's primarily only successful in cases involving negligence that harms the client e.g a leak of sensitive data that makes someone loose an important client.

Lost revenue obviously isn't the reason for it, anyway. It's almost certainly due to technical limitations of their data collection method resulting in them not being able to associate unique installations with their associated license. So the reason devs must accept a degree of inaccuracy that inherently favours Unity is that it would be illegal for Unity to be accurate.

I think that's quite an assumption...... servers cost money, sending a large amount of traffic through them cost money, it's pretty standard for service companies to increase fees with increased server usage.

If I were a guessing guy, I would imagine that being able to track unique downloads would be kinda important for a gaming dev service.