Just to clarify, split is not required. Usually the sight is pretty much bottomed out at 90 meters (100 yards) for a FITA competition; however, Olympic distances are set at 70 meters (77 yards). There is usually quite a bit of room between the aperture of the sight and the arrow as it passes by for competition archers at 70 meters. Most men archers are pulling 40-50 pounds through the clicker, personally, I pull 50 pounds.
Some Olympic archers do touch the string on the nose as a reference point depending on their body structure, draw length, and length of bow, not all do. Personally, I do not. Most everyone does use the string blur on either side of the aperture as a reference (a lot of hunters do as well, I do). I also believe it is correct that under the chin promotes better bio-mechanics and back tension as mentioned in Diamond Paul’s post. However, there are still other styles that I have seen (Asian) that promote even better back tension IMO. However, it is a give and take as I feel there is a loss of precise anchor points.