If by technically you mean literally the definition then yes. It's not technically. It's just the thing. Its the actual definition.

But on the other point anti-competitive practices don't have to be part of a monopoly. They're the easiest way to become a monopoly, steam just did it the hard way. This is what a lot of people fail to get. It's only about the market share. Steam has an overwhelming insurmountable market share, which is kind of the topic of the post that people didn't read I'm guessing.

I'm glad people like Steam. I do too. It has absolutely nothing to do with the topic though. Steam is a Monopoly by definition.