This is probably intentional. The post-destruction-cooldown is only for heavy tanks, and the Command Panther is a premium medium.
okay but maybe it should be considered paying attention to it. Back in the days, Command Panther was the most common request for "please add a timer after destruction" and now after OKW Tiger got nerfed, Spec Ops doctrine became a LOT more popular again.
And why always make these weird exceptions? The mark target allows the Command Panther to 1v1 any other tank in the game with ease -even IS2 and ISU152- and it's limited to one. So just because the Germans categorized it as medium tank in WW2 it shouldn't get the same treatment like a heavy??