When I queried this some years ago with EASA I was told that the 'D' against a single row, as in the case of MEP(L) and MEP(S) class ratings was meant to indicate that differences training was required between all aircraft types within the class. In any case, I notice that there is now a note in Table 1 of the list that reads "difference training is required with every MEP (land) listed in table 10", which seems to remove all doubt.