I agree with you that anything using Steam’s services should be subject to their terms. I don’t think a lot of people are arguing to the contrary about that. I have heard others accuse, though I don’t know with how much basis, that they apply the same control to games not using their infra.

The only example ever floated of them doing this with out steam keys or them being the distribution source was a single email from steam support to a developer. That has been proven over and over to have been a miscommunication and not actually an enforced policy.

If this is true, I definitely agree that they have done nothing wrong. Problem is with the many conflicting stories online and lack of solid info.