Also, it’s not just the numerical quantity that is not properly represented. There is also the quality of the different units. Take tanks for example: The German tank is a Panther, the US tank is a M4 Sherman and the Japanese tank is a Type 95. In the actual war, the Panther clearly outclassed the Sherman and the Sherman totally dominated the Type 95. (In fact, the Type 95 was not a tank by German or US standards).
However, in the game they all attack and defend at 3. Not sure how you would fix the values to show the performance of particular units, but I think you would have to use a D12 system.
Also, like others have pointed out, a tank piece is not just tanks but represents a number of different vehicles like tank destroyers, SP artillery, tanks of varying sizes, etc.
