George, I don't own one but I can tell you what the argument is: Particularly when screwing the cap onto a fountain pen a multi-start thread will reduce the amount of screwing needed to seat the cap. A triple-start thread, for instance, will require only one-third of the turns an equivalent single-start would need. Most kit FPs have quadruple-start threads cap-to-barrel.
As you rightly point out, the consequence of using multi-start is that you need to choose exactly the right start each time to line up any grain or other features on cap and barrel, and do it each time you use it.
You pays your money and you takes your choice ... 
