Obviously phased rollouts are fine and even necessary like you said. That’s not really “experimenting on people”, it’s experimenting on the network/system.

I constantly experiment on users in my work. It’s all around extracting the most money you possibly can. Meanwhile we have mountains of UX interview material where people tell us exactly what’s wrong with our site, and we don’t implement any of it lol.

Profits are up though! In a big way! And our users continue to hate us more and more.