Oh boy, techno-geek!
The pin is often called on to do a job it was never intended to do. Typical machine threads are designed for one thing, to fasten two things together under some level of pressure. Notice there is nothing said about aligning anything or holding anything straight. Machine screw threads aren't designed to do these things. To illustrate just how sloppy and poorly fit together screw threads are, put your cue together but only turn it a couple threads deep. Shake it and the typical thread rattles and the tip will probably flop around several inches. The last screw thread is just as sloppy as the first so we see a flat faced joint on a pool cue with no alignment aid is basically flawed. A pilot, large or small, is needed for precise alignment. We get close enough with the pins because the joint is massively overengineered in a pool cue. Another reason is that most are using a higher quality thread with tighter tolerances than a piece of threaded rod from the hardware store. Years ago I had an order botched by Atlas, botched so badly that it seemed deliberate and I suspected an angry employee. I suppose a green hand could confuse how bins were labeled or something similar but among other things I got the cheap pins and inserts. Not worth shipping back, I threw them in my junk drawer. I think most cue builders would do the same.
Ultimately i planned to go to my own pin for several reasons. One being the same as most that have a unique pin and female thread, I wanted to stand out a little bit and I also wanted to prevent other components from fitting mine. A Hubilt butt and a shaft I didn't make is not a Hubilt cue. Neither is my cue shaft on a different butt. Experience has taught me that most aren't going to mention it is a hybrid and the person trying the cue is going to go away with the thought that is how a Hubilt cue hits. So there are good reasons for the development of a lot of different joints. One is that the builder probably thinks they are building a little better cue, two is to standout a little bit, and three is to prevent the mismatched hybrids I mentioned.
I heard about a master pistolsmith for years. Never got to fondle one of his pistols. When a magazine had a large article and a centerfold of the pistol I scored it instantly! Damn, all these years, and people waiting six or eight years to get one and the gun had a very nasty looking misfit! After a minute's thought I realized that with the gun passing from hand to hand after leaving the builder the fault was probably in somebody else's assembly. I had to think it was a bitter pill for the builder to swallow, the gun featured in an international magazine, looking like a man that just came out of the outhouse with his polka dot drawers showing!
Lots of reasons for the various threads and joint designs used in pool cues, best engineering rarely one of them!
Hu