Hi Nasir,
I see what you are saying regarding the shape and size of the muzzle brake. The question really becomes did the Panzer IV use more than one type of muzzle brake? There was clearly a change between the ball style single baffle brake fitted to the original long barreled Panzer Iv Ausf.F2s and later models. Do you know which models you have posted?
In April 1943, the KwK 40 L/43 was replaced by the longer 75-millimetre (2.95 in) KwK 40 L/48 gun, with a redesigned multi-baffle muzzle brake with improved recoil efficiency.
Here are some different models to compare:
F2
G
H
J
To me it looks like there was a change between G an icsd H which corresponds with the April '43 gun change.