The churhchill croc has 180 rear armor
Panther has 220 Penetration far
Shreks have 160 pen far and 180 pen close.
It's impossible to bounce a rear armor panther shot and shreks bouncing are quite unlucky. Are you sure you hit the rear armor?
That said it is slightly more Rear armor than say the tiger and IS2 both at 140, or the King tiger at 150. It is the same as other churchill variants at 180.
I am %100 sure i hit the rear armor.
Edit : But ingame rear armor and front armor shots are quite buggy tho maybe thats the reason. But there is no point of that much HP and armor on a flamethrowing tank that can change to main gun instantly.