The UK treats the regulation as it is written, if not we would soon run out of examiners. An ATPL holder would need the same Instructor/Examiner certificates to train and examine PPL as a CPL or PPL holder. To examine, the Examiner must hold a qualifcation at least equal to that which he is examining for. So if examining for a licence then the Examiner must hold that licence, but in the case of a rating, they must hold the rating, Type, Class or IR.