I think they are referring to this basic requirement for all examiners:
”hold an equivalent licence, rating or certificate to the ones for which they are authorised to conduct skill tests, proficiency checks or assessments of competence and the privilege to instruct for them”...
However, I would say that this test is not for the licence but for the rating and so he should not need to be an ATPL. In fact, somebody who only has R44 experience (and other non-MPH types) could not hold an ATPL anyway. It can also be done by an FE, not just a TRE.