Isg cost 55 fuel to unlock tho, doesn’t have green cover, has 40 les barrage range , it’s has lower aoe than a mortar, all in all the isg is a more expensive and worse pm41 the Soviet base mortar
The two models behind the unit are effectively in Green Cover.
Not to mention they have a target size of 1 as opposed to a target size of 1.25 on the packhowie.
It has low aoe but high rate of fire and good accuracy and it's cost makes it spammable as OKW is really good on manpower if you can micro.