I just had an game where I was backing off and a leopard shot me in my commander’s cupola with DM12. The round instantly overpressured and took out my entire crew, including the driver. I’m not certain why this happened, but it is 100% reproducable in protection analysis. Just take an Abrams (this happened to me in the M1 KVT, but it seems most Abrams variants are susceptable to this), and shoot DM12 at the commander’s cupola, more or less parallel to the turret roof. The should kill the entire turret crew and possibly the driver, depending on the variant.
Seemed bit weird, so i went to check the armor protection analysis and what do you know, HEAT shells (tested with DM12 and russian 3BK18M) do in fact overpressure the turret roof on most abrams tanks (failed to replicate the issue with M1A2, HC and SEPv1, where it only kills commander).
105mm Abrams, 120S and M1A1 are the worst as even driver dies after hit to the same exact place with commanders copula.
I also went to test drive with turms and fired few shots at the M1A1HC. The plasma stream will either detonate the ammo in the back of the turret, or only kill the commander.
all and all seems bit inconsistent, would advise you to make a bug report to be sure.