I don't own 44 mm sandwich dials so I am guessing but. Dial, underdial or both may be thinner. Certainly the case on the Fiddy. Presumably the movement is in the same place in a case on a better rep (overall height and crown positioning)and it is the same height movement. The other possibilities are thinner crystal soaking up less rehaut on the rep, overall bezel height and internal height (think of it as visual carve out in the bezel).