An instinctive shot happened the first time you loosed an arrow. From that point on, adjustments are made, whether consciously or not, until satisfactory results happen. It is a conditioning process.
According to Bob Wesley, another HH "favorite" protege from Mississippi who became a world champion longbow shooter and teaches "How to hit like Howard Hill," Hill used a point of aim/split vision method of aiming. Wesley uses and teaches that method.
For many of us, improvement in accuracy comes slowly as we work to build a solid shooting foundation/form. Developing the "feel" of proper back tension before the release is the part of the shot that can be elusive. Once that happens, though, the bow arm will stay up and pointed at the target throughout the shot and, if the bow/arrows are tuned properly, windage is dialed in. Then it's a matter of developing the "sight picture" that allows for distance control. That is where point of aim/split vision/gap or "instinctive" shooting come into play.
We all want to be as accurate as possible with our bows and arrows. Some of us are blessed with more natural talent to do so than others. Kinda like comparing an "average Joe" basketball player to Michael Jordan. So, we "average Joe" guys resort to various aiming techniques to get us closer to our goal. We enjoy the heck out of hunting with a bow and want to make sure that when we loose an arrow at a living target that we can place the arrow where it will rsult in a quick, humane kill.