I'd attribute it to well matched arrows. I seldom spend more time than that with tuning (after I've spined tuned my arrows). I find that most tuning problems (assuming no bow defects), are due to arrows that are not ideal for the setup.

I will admit to spending a lot of time getting my arrows just right. Most bowhunters spend about 5 seconds tuning their arrows. I spend 2-3 hours on that portion of tuning.