That's just seems to be something specific to this site that you have found. Personally, being on tumblr and Youtube, I have found that the majority of people opted for Alpha Sapphire. Marriland and Pimpnite both did Alpha Sapphire tutorials, rather than Omega Ruby; Kynimdraws & Protocol00 both played Alpha Sapphire..
Also there are version exclusive Pokemon, not least the cover legendaries, that might have influenced people's choices, e.g. Mawile is exclusive to OR and Sableye is exclusive to AS.
So in conclusion, it's really just coincidence.