A quick explanation might be gaijin’s method of dealing with OP SPAA - moving them up in BR. We’re seeing this live with the Coelian, which got its absurd APHE buff and was “fixed” by moving it up to a higher BR (which is actually more of a buff as 7.0 starts seeing lighter pre-MBT vehicles). Add this onto the “French tax”, which is a popular coping mechanism involving France players apparently being so good all their vehicles are at least 1 BR step higher than they should usually be, and you have your answer.
Realistically? I think gaijin saw a full belt of APDS and decided to move it up, as they do like to focus on a particular aspect of a vehicle as justification rather than considering its all-around capabilities. The stabiliser doesn’t matter all too much given that with how slow you are sometimes, the traverse essentially serves that purpose.