What I'm questioning is whether any Standard (BS 7671 or otherwise) relating to the required performance of a product (i.e. passing specified tests) can say that a product does not conform to the Standard if it passes all the tests etc. but does not have some marking on it.
FGS.
BS 7671 is
NOT saying that an MF accessory does not conform with BS 5733 unless it has some sort of marking. It is saying that to
conform with BS 7671 the accessory must conform with BS 5733
AND have some sort of marking.
Just like it does
NOT say that a "combustible" CU does not conform with BS EN 61439-3, it says that to
conform with BS 7671 the CU must conform with BS EN 61439-3
AND be "non-combustible".
I could extend/modify an old installation using harmonised cable, and I could use materials which fully conform with all of their appropriate standards, not one of which involves sticking a label on to warn of mixed colours, but
to conform with BS 7671 I do have to apply such a notice.
I really do not understand why you struggle so with the concept that BS 7671 can require A + B without that creating a requirement that A also requires B.
As I've said, it's fair enough for legislation/regulations to 'require' that a product conforming to a particular Standard should bear a marking indicating that conformation,
Well unless you want to claim that
526.3(vi) contains a tautology, that is exactly, and only, what BS 7671 is doing.
but I am far less sure that it is possible (or appropriate) for a Standard to say that a product which otherwise would conform does not conform because it doesn't have a particular marking.
Well unless you want to claim that
526.3(vi) contains a tautology, BS 7671 is recognising the situation that an otherwise BS 5733 conformant product does not have to have a particular marking to conform with BS 5733.