Agreed , killing a main battle tank from second half of ww2 with .50 cal or even 20mm where very uncommon.
They could damage individual parts like track or engine or individual crew-members though.
An 23mm Il2 would penetrate top armour if they had close to 90 degree angle on it only IRL.
German attack planes would almost always go for the soft targets so tanks could not refuel/re ammo because it was much easier and made the tanks stop their advance. Only with bombs/rockets could they get any hope of killing them except the 37mm Stuka.
A more granular GV damage model is much needed IMO.