NOPE, It is because risers are not parralel with the powerstroke.There is even a product on the market now to set the fourth axis because most will set the 3rd axis up to the sight bar(put level on sight bar), but when they bolt it to the bow,it is not square with the arrow(power stroke if centershot is correct)

Therfore,the need for the fourth axis.It bolts on to the riser and the sight bolts to it,the sight stays square with the sight bar,then you adjust the whole sight torun parralel and squarewith the arrow or powerstroke,or centershot,however you want to say it.[8D]

I saw about a 20 page deliberation(argument) on this subject alone on Archertalk a while back.MOST just couldn't understand this.