Well aren't we told to follow manufacturers data/instructions when a conflict exists?? The reason why manufacturers tables and BS7671 tables often differ, is BS 7671 tables often try to cover a group of similar cables in a single table. Unless were talking about an unknown cable manufacturer from some back and beyond country, compliance to the Reg's shouldn't be a problem...
Whilst i agree with you on the EICR argument, i'd tend to put more faith on the actual manufacturers cable data tables, than that of anything produced in BS7671.
I would also state, that anyone here that isn't fully competent to make such assessments between cable manufacturers tables and BS/Reg's tables, should always refer to BS 7671, as you will then always be in compliance!!