FWIW, I've previously owned a bass with a spoke wheel adjuster where the holes were NOT drilled all the way through. They were more like "cups", which would be similar to your situation where the truss rod is essentially the bottom of the cup so to speak.Here's the follow up to my post above...
I never had a problem adjusting the rod at all, but I can see how in your case it might seem odd that the truss rod is visible like that.
IMHO, I wouldn't worry about it at all unless it actually becomes a functional problem. Meanwhile, play the hell out of it and enjoy.