V-Create Rayquaza is actually an interesting story. According to Serebii's Eventdex, it was only released once in Japan back in 2012 in response to a popularity poll. After digging for a bit, I found an article written at the time when the poll's results, and the Rayquaza, were announced by TPC. I guess as a reward for topping the charts, they decided it would be cool if they distributed a Rayquaza that came with the highest base-power move in the game other than Self-Destruct and Explosion (and now Z-Moves, but they weren't a thing back then).