Most of these methods are meant for internal use and don't really have an intended use by end users or extension gem developers.  The one exception I can think of is `reset` -- I think I saw discussion of it being used for an alternate parallel runner at some point.

That said, `RSpec.world` is itself labeled as private (see 1354f1afca8fdc94397daac11255320cd538547c, where it was labeled that way).

I think the class as a whole should be labeled `@api private`.  Anything that's actually needed as a public API should be exposed off of `RSpec.`, and all the private APIs off of `RSpec.` should be removed so that `RSpec.` is the global entry point for the public APIs.