It make a lot of difference. Moving your at gun is not a wise choice consider the terrain regularly make the at gun become bouncy. Not to mention it is frustrating to constantly move the gun.
Your point is there is little amount of people using engineer squad, but then you said it should not be buff if there is more people using it. The two statement are contradicting each other.
You claim engineer squad don’t need heavy at gun to counter grey zone tank.
But apparently the example you give are for Germany.
US and Japan still need heavy at gun to counter grey zone tank.
Not sure why are you bringing tier to this discussion?
Anyway, letting high br engineer squad build the heavy at literally solve the problem.