Even LNAV/VNAV is old now, the newfangled thing for boeings is IAN. Everything is flown with identical procedures and indications, be it ILS, GLS, or any kind of NPA.
That said we do not add 50ft to the MDA, however we have to initiate the go around latest 50 feet above an MDA, if a DA is used instead no added safety margin is needed. Sadly the 50' above an MDA thing is put into a small note that is very easy to miss, simply bad presentation in our present manuals.