I learned " instinctive". But! the only difference between instinctive and gap is whether we're using the subconscious or conscious part of our brain. As stated, our brain is constantly at work in some way or another. When we shoot instinctive, WE are not consciously thinking about yardage and gaps, but our brain is calculating trajectories learned from shooting like this. Gap shooting shooting all we're doing is making the shot a conscious thought, which works great when shooting at a stationary target, not quite so well with game, but still usable.
A good technique I've learned useing a gap method to better train the brain for those instinctual shots is start at 5 yrds, shoot. buulseye, move back 5 yrds, repeat. Miss at 5, adjust gap until 10 ring, move back 5 yards. By moving back only when the target is struck exactly where you want/need. allows the brain to fully understand the trajectory needed for that set up. Set up changes? go back start the process over, until you've gone back to however far back you feel comfortable shooting at game. But I highly suggest to push that learned distance back further than that. Then, when a shot presents itself. Little or no conscious thought is really needed, The brain has it all under control. do this same sequence shooting uphill, downhill, side-hill, any possible shot circumstances, and I promise, your instinctive shots will improve greatly.
Hutch