True. However, in practice, one has to consider the "for an easy/quiet life" aspect. I suspect that quite a lot of argument (not necessarily successful) would be required after someone had conducted an EICR on an installation that used cable which was too small in relation to that 'informative' Appendix, no matter what other data or argument one had to offer to support what had been done (and, of course, the person who 'did it', hence might have some arguments, would usually be "long gone")! As is so often the case, the problem is that BS7671 does not satisfactorily define what it means by CCC/Iz - the definition in Part 2 is too vague to be of any use.As you have already pointed out, Appendix 4 is only Informative. Therefore it does not form part of BS 7671:2008 (2015).
Kind Regards, John