I agree with the idea of NOT turning a perfectly straight pen body . The fountain pens that I just turned are a perfect example of this . All the pictures and directions say that they should be turned perfectly straight from one end to the other (very bland) instead I've turned them with a slight curve to the barrels which , IMHO , gives them some depth .
As for the design of the top pen , I've been turning mine like that for a long time now . I find that with a pen that has an extremely fine finish , tends to slide up more in the hands of the user and the small "lip" on the bottom prevents this from happening without having to exert extra pressure on the pen body . When someone looks at the design of the pens , I always have a straight cut pen handy and have them try both for comfort and most agree that the lipped ones are far more comfortable to use .