I have seen that in several places. 5DIII hands down is better at video. I never shoot video except the odd family thing, so it's a bonus for me. I don't even know what moire is, or why it's bad
Actually a few months ago, when I was considering cameras and the 6D was in preorder stage, I looked heavily at a Mark III and decided against it because I felt most of the upgrades were in the video department, with the significant exception of the autofocus system.
So in short I agree with the article, if you are serious about video, 6D is a worse choice than the 5DIII. I just used the flip side of that argument in my decision-making; since I don't care about video, I didn't want a 5DIII as I'd be paying for features I'd never use, honestly, including the AF system.
The day I decide to blow a bunch of cash on a camera just to have it, it will be a 1D series camera