You're not wrong about the realism of the matter, however your logic is still flawed.
For that to be true, then the 88mm L/71, as well as the armor for the Tiger II and Jagdpanther must be functionally different from the rest of the game, including the vehicles added after Tiger II.
I've been in a Hetzer, and taken some significant number of hits over 27, as I only started counting after it was getting nuts. Point being, the Hetzer does not function similarly to the way you claim the Jagdpanther and Tiger II do with 88mm hits, despite being added WITH the Jagdpanther.
Add to it the fact that HTC said nothing of any such system upon adding the vehicles in question, and the only logical conclusion is that they are functionally identical to the rest of the set, and that the much simpler explanation is in fact the truth.
If you want, we can test this in the DA sometime. The Panther has similar penetration at point blank range to the L/71 at 2000m. I'll up a Panther and bounce shells off your front until either you are convinced, or a miracle happens and I end up killing myself with my own ricochet.