So even if this unit performs well against the 120mm you have to rememeber that it forces the germans into a doctrine and puts them at a disadvantage fuel wise.
120mm is also doctrinal so cant really counter by saying MHT is.
Also 40 fuel are you been serious that's nothing in general + considering its 50 fuel just to give the conscripts the same abilities grens get from start and soviet teching costs more so its not really alot.
Also I could argue that the 120mm costs alot more MP. They are different units that perform different roles and have different costs there not supposed to face of against one another. People compare units like for like all the time when that's not how it works otherwise we would have two identical factions.
MHT may not have the same range but its easier to move around and less vulnerable and has the flame ability which is amazing for preventing caps, destroying MG/AT gun encampments, buildings and blocking areas to infantry.