I watched the video. It's really trying to trace out the arc of adult video games in the US more-broadly than Steam. He does talk about some of the Steam stuff too, which is a little more than just "didn't allow than allow".
That being said, I feel like I would have enjoyed the video more with fewer joke visuals thrown up. Also, I feel like the coverage is uneven...like, it could have done with more research, I think.
It's US-centric, which is fine, but he does reference Japan vaguely. I think it might be interesting to see what was going on other places for context.
It's also fairly-focused on the commercial side of things (which I guess sort of makes sense, since Steam is primarily about distribution of commercial games, though there are also noncommercial games on Steam).