If we're talking about "what the regulation actually says" (or does not say), as BAS often used to point out, the regulation does not say that "only accessories to BS 1363 may be supplied by a 30/32A ring circuit using 2.5mm² cabling".
Apart from anything else, as EFLI has said, that interpretation would mean that, for example, the 20A grid (or plate) switches commonly connected to kitchen rings would be non-compliant.
Kind Regards, John