Apologies for that, I was thinking of the old rules. BUT re-read the extract above, a1and b rely on flying at speeds allowing avoidance of other traffic or OBSTACLES, OBSTACLES tend to be terrain based, they are rarely hanging around at FL90. The terminology is poor in 5005, but sight of the surface is implicit in the avoidance of obstacle wording. The UK ANO and JAR were clearer on this, SERA 5005 gives intent in it's wording, but needs clarity.
SND