What is a 'round down'?
The 'Round Down/Rounddown' is literally the after deck edge of the carrier's flight deck, aerodynamically shaped to reduce turbulence encountered by approaching CTOL aircraft as they come in to land. STOVL carriers don't have them as Harriers normally approach alongside the ship in hover mode and match speed with the deck, then 'translate' sideways over the ship and touch down vertically. CVF as designed had a CTOL style round down fitted aft so that if and when the ships are brought up to CTOL standard it will just be a matter of installing the arrestor wires and catapults (which the ships are already designed to accomodate, ie 'fitted for but not with') then painting the angled deck onto the ships. Omitting this feature from the ships now does not preclude re installing at a later date, and as I said earlier, is most likely a cosmetic measure intended to appease the bean counters without actually sacrificing any capability.