Surprisingly, I think everything above is correct!
The GR1/4 does not have functioning ramps. However, the ramps (if they were functioning) do not start to move until about M1.3 so don't actually make a difference until then.
A GR4 will still go super but as you hang more stuff off it it becomes harder and harder, until at some point it can't. Additionally many stores may have a VNE or MNE that limits the ac to a slower speed than it may be capable of. I guess a GR4 guy could give more details.
As an example from the F3 world the M fit tanks have a subsonic limit on them but definitely do go super (I've seen it, but not done it, honest!). The F3 also does have functioning ramps, and they have a noticeable affect as soon as they move - giving decent M1.3 onwards acceleration.
Even old, bent F3s can still get to Mach 2 with inboard pylons and stubs fitted. Clean ones certainly quicker, but of course that isnt allowed so noone has done it.
Hope that helps