Maybe we can discuss nock points so all of us can understand the terms and what is happening.
From my thoughts. . When you place a bow square on your string, the lower edge makes contact with the shelf when it is in correct position. That means the lower edge of the square, where it meets the string, represents the bottom of the arrow.
The arrow itself (at the nock) has some width. If you place your nock set at "0",and nock your arrow below that, it means the arrow is positioned below horizontal.
If the nock set is set at 1/4"(about the width of the nock)it makes your arrow sit about level. (Remember, If you are using Easton 25/64 shafts, or anything else over 1/4" wide, the 1/4" noted above is still not enough to make the arrow sit horizontal).
Draw that level arrow back 28" and the angle of the string changes that some more, likely lowering it a bit. Again, that makes it below horizontal at the start of the push. The longer the draw, the more severe the angle and the lower the arrow rides. All depending upon your finger placement at anchor.
By placing the nock set above 1/4" (or the thickness of the nock/arrow shaft)it starts to align the arrow slightly above horizontal. This is what is trying to be achieved.
Some set ups may need to be an inch high or even a tad more than that, but 3/8" to 5/8" probably covers most set ups. It appears to me that those with really long draws tend toward needing higher nock points.
ChuckC