I think you will find top tubes on MTB's are longer.. so stem has to be shorter with drop bars..

I have converted to Trekking bars, they work as a simpler touring adaptation of MTBs
because the tube is the same as MTB bars [1"center, 7/8" rest of the bar],
so you don't have to swap out the whole kit
Stem, bars, levers brake and shift, 4 cables, and housing, grips> tape, and all that..

brake levers can go on the inside rear center of trekking bars, slip right on.
with open face stems
you can take them out without disturbing the grip-sleeves or tape job,

useful in pre trip packing..