There were no changes between MBT and WW2 in the arty (some think the blast circles are new, but they are not and have been there all the time - we just added a switch (originally just for debug, but we allowed this for the end user as the playtesters liked it
) to show the circles graphically.
I will monitor this thread and see what the consensus is. But it is possibly because the armour in WW2 (esp top armour) tends to be thinner than in MBT. And many open-topped "shell spitoons" exist.
Anecdote: The first Royal Tiger kill in Normandy was with a 2 inch mortar. The guys who fired it cannot agree if the tiddly little 2lb bomb went straight down the turret hatch or simply into the ammo truck it was parked beside and replenishing from. Either way - the turret was lifted by an internal explosion, a halftrack nearby was abandoned, and the other Royal Tiger exited the village sharpish! .
Cheers
Andy