Ive already explained it.
This tank was never planned to come since its an incomplete prototype tank, something we generally dont add to War Thunder and in fact removed one in the case of the Flak 341.
However, many made it clear they would like to see more indigenous designs for Italy in general, including this one which is very close to the mark of whats possible in game. So we listened to that feedback and this is the result of that.
Given how only 1 incomplete prototype was created (and not fully finished), coupled with the fact this vehicle is not very well known outside of the Italian tanker community, most players would not really find it a significant addition and likely just skip over it if it were in the tree. Plus there really should not be huge numbers of these running around unlike a Panzer IV, Sherman or T-34.
Part of the reason its even coming in the first place is directly because of people wanting more Italian designs. But this one is better suited as a premium since only 1 was made and it was not even fully finished.