He could have gotten 100% correct if he'd had more patience with his material.
You don't remember him insisting that Luke was the villain of the story? He went to great lengths to cram what was known of Hammill/Luke into what was known from production art and story leaks, and indicated that the images of Ren (whose name was not known at the time) represented Hammill. With each post and tweet and message board conversation, he became more insistent that this was the direction of the story. It was all based on his own speculation (as usual) informed by drawings and bits of information, but when people took Occam's razor to his theory he dug in his heels. He said Hammill's beard was contractually-obligated (borrowing from Hammill's interview joke) was a ruse; that he was following the production to Ireland, to England, to California, all in the fake off-hours beard, to throw off fans - all in bizarre support of his own guess at what all those pieces might be pointing to.
This was the beginning of it: http://makingstarwars.net/2014/10/huge-rumor-star-wars-episode-viis-father-sized-moment/
It's par for the course - you're rolling the dice reading their news, and Jason's attempts to mislead his competition (and their readers) are contrary to the spirit of the fan community that I would encourage. MSW won't get my clicks or support.
Ok yes, he led with a rumor of Mark being the villain. But he never said Mark was the Kylo character. That's always been Adam Driver. He did at one point speculate if Luke was portrayed as a half cyborg in some of the concept art. And yes that was incorrect. I am agnostic towards all of this. I don't care if Jason is a class one tool, I'm just curious in collating rumors and seeing which pan out. And a sober, unbiased anaylsis of what we have heard so far still but the ball in his court regarding veracity.