I'm the Wikipedia editor who originally proposed this change. To avoid confusion, I think it should be clarified that "within userspace" is meant to refer to an individual editor's own userspace, not the entirety of "userspace" among all editors. In other words, the intention is for editors to have the "suppressredirect" and "move-subpages" privileges only when both the origin and the destination of the moved page(s) are within that user's own userspace — not those of other users, and not in other namespaces.