I agree, its damn stupid that the p4 has 110 pen while sherman AP and cromwell have 120. Especially as even in the model you can see that p4s gun is longer barreled and thus should have better pen. I would even suggest buffing p4 to 120 pen while nerfing cromwell and sherman to 110 at the same time.
the penetration on the sherman got buffed because no one ever use it into the late game. Unfortunately people still never use it into the late game because it have bad survivability. Even the british are abandoning their cromwell for the comet since the cromwell is a lot easier to kill now.
ironically the t34/76 "scale" better since it's so cheap.