no one crosses the MDA and then goes missed, what are you talking about?
You have to figure your momentary descent so when you go missed, you dont go below the MDA...it is a glass ceiling...Chances are, your momentary descent is more than 50 feet, so when you have an MDA, you have to calc your minima so you dont bust the MDA.
I would be very curious which operator has the MDA and DA at the same altitude.
MDA can NEVER be the same as DA.