as I promised in the comment section, got my investigating feet on the odd WZ-111 HD model and got an answer today.
But first let me explain everything:
When I was doing screenshots of the WZ-111 in HD I've noticed the huge gun difference and checked straight ahead the latest WZ-111 modules and statistics but there were no changes made to the tank which was very weird as the model in Sketchfab has been added 2 weeks ago.
Then I started thinking... if its the premium WZ-111 and the gun stats haven't changed to such a massive difference between SD and HD then it could be the WZ-111 model 1-4 with the WZ-111 turret.
Its usual for WG to miscall their tank names, I never bothered to write about that on the blog as its not of importance and because I always make sure to privately give them a nudge and to be honest both tanks are extremely similar, it would have been a understandable mistake.
BUT even the WZ-111 model 1-4 guns don't coincide with the gun shown on Sketchfab.
The gun has the muzzle of the stock 100 mm 62-100T but the length of the 130 mm 59-130T of the WZ-111 model 1-4.
I hit a dead end so contacted MrConway, a new Community Manager for EN/EU to get a hold of the right persons and apparently I was indeed right to pressure on this matter.
Basically what happened is that its the right tank, the WZ-111, but during assembly the tank had 4 guns available and the wrong one was applied accidentally, but only on Sketchfab.
WG has thanked and it will be fixing it.
I will make sure to share with you once is fixed if the official screenshots don't come earlier.
Also, thanks for your guidance in the comment section, it always helps. :)