FF
The AIP is not the law. Only the ANO is the law (in this context).
Also, phrases like "first obtain an accurate fix" are a give-away that this is an informal piece. What is an "accurate" fix??
If you have enough time to thumb through every piece of paper that's ever emanated from the CAA (AIP, AIC, all the wonderful differently coloured supplements like Pink and Mauve) you can find just about anything. You will find something that makes GPS illegal, if you look hard enough.
Incidentally, a radar altimeter does look slightly foward.