Yes. I ran this entire thing for you to see that it doesn't work that way and even installed bandicam and uploaded it to youtube only for you. You can clearly see 2 shots are deflecting and it is not 100% penetration.
https://youtu.be/xmvpIaIK_Hw
As I had to learn myself, frontal armor is not just the front, but the front half of the vehicle. The frontal half of the side armor is seen as "front armor". Therefore, the right StuG is always hitting the front armor, the left one is hitting the rear armor. That's why there is no "rear armor hit" pop up when the right one fires.
But the StuG doesn't kill via high penetration, it kills via high ROF, especially when vetted.
The StuG vs rear armor is overall a not very realistic scenario overall though.