I think your assumptions are extreme but you also do not include duration of the shock wave. Studies show the brain can tolerate very high Gs, in the 200 to 400 G range for milliseconds.

But, I think you are grossly missing how much distortion exists in the elbows, shoulders, and neck.

Still, 30 Gs is likely just a subconcussive impact that, alone, with time to let the brain recover before another impact, is of little consequence.

The whiplash to the neck would likely be most of if not almost all of the trauma.

UPMC studies suggest 80% of concussion symptoms are neck/whiplash related.