That's a weird one for sure.........The view of him walking straight away is a good one.
The problem with the not getting inot the body cavity thing is the rounded contour of the body as it slopes from point of impact to the exit hole.
If you draw a straight line between the 2 on the pic of the deer walking straight away , and assuming the arrow stayed straight since the blades didn't cut the skin it had to be maybe what 1/2" into the body to keep the blades from peeling the skin back?

Hard to say what did or didn't get hit but if it was something vascular like the main artery along the spine or kidney even if it was a nick the deer would be dead after 3 or 4 days or whatever it was?

Could it have nicked the intestine? I guess..............He certainly looks pretty chipper. No hunched over feel or lack of energy which would indicate him being sick in any way.
Arrows can do funny things in the body at impact.......just ask Pat Reeves on that big Wisconsin monster he thought he smoked.

You can rule out a couple compromised vital body parts just by the fact the deer is alive, no spinal cord damage, no major vessel damage, no kidney damage...........not sure about intestine though and the self healing properties if they were even hit.

Just another example of how tough these animals are and how comparatively wimpy we really are.

I wonder what broadhead he was using?