I bet the same thing happened.
The thing with the german tanks, besides the Panther and King Tiger, they all did look somewhat similar. III, IV, and Tigers all had the "box" look, straight armor, similar stowage bins on the rear of the turrets, etc. This was one of the factors that led to so much mis-identification. I think I read somewhere- if we were to take American combat reports from the Normandy campaign at face value, the Germans would have had a larger number of Tiger tanks serving in Normandy than they actually manufactered during the whole war!
In the case of the germans mis-identifying russian tanks, that's a really good point. And probably impossible to actually pin down! The russian information I've seen is often very spotty on production and service numbers, so it is difficult to begin with figuring out how many of what tank was serving in which are at a given time (
). It is somewhat simpler in the case of the russians though- we are really only talking about 2 or 3 types of tank. The T-34 had many minor variations, but they all outwardly looked alike. Same with the KV series. Once 1944 rolled around, you start seeing significant numbers of T-34/85s and IS tanks. Starting in 1941, the T-34 was introduced in huge numbers.
So I guess it would be impossible to get any real numbers for german mis-identification. I'd guess it happened less than American mis-identification though...