…and installing Steam is the route you want to use to do that?

Not at all, and that’s a good point that it’d make sense for a package manager to somehow discern someone doing install steam from ones doing purge gnome-desktop. But then, if the first resolves to the latter, something has already gone catastrophically wrong, any action here would be a stop-gap, which this whole “do as I say” thing essentially was. The good thing, at least, is that it’s in our hands to come up with a better solution and propose it in a form of pull request.