Red Plum, what you are quoting is the Guidance Material (GM) of SERA that explains, a contrario, that when above 3000 ft AMSL (or 1000 ft AGL) maintaining sight of the surface is no more required and thus VFR on top is possible.
The actual SERA requirement states that, below 3000 ft AMSL (or 1000 ft AGL), keeping sight of the surface is mandatory.
Originally Posted by SERA.5005(a)(iii)
(iii) in airspace classes B, C, D, E, F and G, at and below 900 m (3 000 ft) AMSL or 300 m (1 000 ft) above terrain, whichever is the higher, the pilot shall maintain continuous sight of the surface; and’;
Sera regulation writers have played the same game as FAR authors : what is not explicitly forbidden is permitted.