I upgraded my xl with belt z to z-plus. At the bottom of z-plus is a rod with a hole in it. The ball screw does not come within a 1/8 inch above the hole. I know what guides the ball screw is the block higher up but should the ball screw be long enough to go through the stud with the hole in it?
No, it is the same. Long story why there is a hole in the Z minus Stop Pin (What you call "stud). and I won’t go into the details…but it does not go through the stop pin, there is NO need for it to go through it either. All is good.
But it bothered me…so I made a little bushing for mine to make my engineering brain (ADHD??) a little happier.
The cylindrical post is simply a stop, and the hole is in it to ease fitment and ensure that nothing interferes. A bushing such as @RichCournoyer shows is purely an aesthetic option and has no affect on function — the leadscrew is too short and the linear rail system too secure for whipping to be an issue.