The theory behind reversing a squat suit is more based on the old z and Champion suits. By reversing it you switch the seam on the strap to further behind the trap which was thought to help in keeping a lifter more upright when they pull.
With today's suits, for example a centurion, the same thing can be accomplished by tightening up the straps (like I have said before a poly DL suit should be shorter and somewhat wider than a squat suit becuase if you can tolerate it you will get more pop from tight straps whereas overly tight hips will cause problems with reaching the bar) and pulling the seam as far behind the trap as possible. This is why if you are altering the straps, leaving them with a tab sticking out will give you something to grab and make placement of the seam on the lifter easier.
The problem with the older generation suits is the material was much more stretchy and your ability to set the straps and have them stay was not good. If I remember correctly (don't have a z-suit anymore to look at) the seam was placed so that the strap was shorter in the front relative to seam position. Turning it around moved it behind the trap which is what you want. You want to effectively make the straps shorter in the back of the lifter which pulls them more upright.