I can't answer for HTC, though this matter is not a new one, a couple of straight forward answers could help with an explanation, even if were not the official or 100% accurate one.
Two things that I can recall were discussed in the past. 1) A round strikes the object and does not hit critical component, and thus tank is fully operational. 2nd) A round strikes the object and is deflected by the armor and / or slope of armor doing its job, and thus tank is fully operational.
In your film, I don't know if it is possible to detect nearby supplies or not, but that presents a possible 3rd answer for multiple hits on a still operational tank. Having said above that there are reasonable explanations, I will still gamble there are far more forces involved, and some may not give us the results that we would hope they would, but for the most part, things work the way one would think they would with some exceptions.