"Don't see your point. Providing you fulfill VFR separation from cloud you can be VFR "on top". If you're above 3000ft certain parts of those criteria are increased, but still applicable.
Where does the "800ft above the base" come in?"
My point was that if you are 800 feet above solid cloud but in VMC can you fulfill the VFR criteria. If you cannot you presumably can only be IFR.
In the same way if you are at our below 3,000 feet above cloud in VMC you are not in sight of the surface. Can you fulfill the VRF criteria?