It is hardly an 'interpretation'. FCL.720.A(f) quite clearly states, "An applicant for the issue of additional multi-pilot type ratings and single-pilot high performance complex aeroplanes type ratings shall hold a multi-engine IR(A)". Examples of ATOs setting non-compliant requirements should be appealed to the competent authority issuing the approval. I have, in the past, recommended this action to a number of candidates with considerable success.