The MSE-3 Marid has a similar issue, none of the crew can be hit by outside sources even though the passengers can. Tank shots to be lethal to all crew inside vehicles in cases where the armor doesn't deflect the shot (by being at a steep angle or being thick enough to absorb the impact)
Additionally, tanks added in the full release should be tuned to follow the same rules. A clear shot through any of the crew inside a MBT, even if rare, should kill the people inside, which would add some depth to tank combat in ARMA as angling the armor against an attacker would be an effective way to increase crew survivality.