Guilty as charged HB, pardon me doubting then. Out of interest, given your "theatre" could your outfit actually do without it?
Murky side story: there is a HW/SW configuration of quite a few airframes, where for a LNAV+VNAV managed app mode executed with QNH you need to set (M)DHinto the FMS for all things to work. While with the same ship, on a non-VNAV apch, (M)DA goes into the box.