Why the hell is a KV-1 a medium tank and a BT-7 too

yeah i get it,they may have filled the void during the time,but the bt-7 was a light tank and the kv-1 was definetly a heavy tank,instead of using those two tanks as medium,use the different variations of the T-34 such as the early 1940 model with the L-11 and then the level three medium could be say the 42' variant with the hexagon turret (of course the level one medium tank would indefinetly be a T-2 and then the level one heavy tank could be a T-35,the lvl 2 one could be a KV-1/2,then jump to the IS Series,the premium or whatever it's called light tank (lvl5) could be a T-50 although less numbers than the T-70 were made,they were technically early t-34/A-20s,the level 4 one could be a t-70 instead of a t-60 as they were much weaker,instead of the T-37 which was a amphibiou tank armed with a 7.62MM DT-29,that could be the t-60 with the 20MM TNSH cannon

i am talking about the research tree as such

dunno what else to add so yeah