I was just doing an exhaustive search for the word "solo" in LASORS and hit upon the same article.
But... The whole of section C3 applies to Gyroplanes. There is no comparable requirement in section C1 (Aeroplanes) or C2 (Helicopters).
Nor in section C4 (Balloons, Airships) or C6 (Microlights etc) for that matter. I wonder what's so special about Gyroplanes that the ANO would requires Air Law (plus a few others actually) before first solo there, but not for any other aircraft type.