Definitely Lusche. When the Tiger came out I had an M3 run by me and take 3-4 shots in the process. I couldn't believe it at first so I used the other type of ammo than what I'd first scored hits with, but it made no difference.
So I asked HT in the next blue Q&A session whether light GVs should recoil somehow from a high velocity impact somewhere else than the empty sheetmetal, e.g. in the drivetrain parts or something. He said he'd have to run some numbers, and that's the last I heard of it.
It might be some bug, because now it's pretty easy to kill GVs with an HE round's splash damage. I recently had an M3 hide right behind the VH near a vbase's map room, and killed it by shooting the corner of the VH it was next to.