Im sorry that you were under the impression that there was no official rules regarding priority.
Official rules regarding priority do exist. The basics regarding them can be found in the Yugioh TCG Official Rulebook (version 7.0).
More complex rules surrounding priority can be found here on this forum, on the Judges List, and in my guide to priority, which is based directly upon research into the advanced gameplay FAQ, basic gameplay FAQ, the official rulebook, and upon hundreds of individual card rulings that I have researched over the last 4 years.
Trust me when I say this....
Any information you hear regarding priority from an expert in the game, of which there are numerous such experts on this forum - Ryoutaro, Illusion, D1Case, Myself, Robert Wakeman, Franklin, and John Danker just to name a few, will be FACT, as each of us have many years of experience under our belts, and know this information inside and out.
In fact, the complexities of Chain Construction including (but not limited to) Priority happens to be my strongest area of expertise (of which there are few on this forum who know more), as anyone on this forum can verify.
Were this not the case, I would not have 3 articles stickied on the first page of the Unofficial Rules Forum dealing with this very subject in different situations.
No one's been able to take me seriously... But that will change when I beat you at a children's card game.