One have two major qualms about GAF insiders including Mort:
1. They aren't insiders and they know far less than any actual insider does.
2. At this point anyone talking to Mort has to know that he is going to share that info with everyone, which calls into question their motivation and also makes it very easy to use him as a conduit for information they want public.
That first issue is just one of somewhat misleading billing. The second one is the key. Judith Miller repeated Iraq information from anonymous sources that told her exactly what she wanted to hear and exactly what they wanted the public to hear. In short she was used, or allowed herself to be used, to convey messages to the public as part of a PR campaign.
When someone tells Mort than the XB1 is unstable and crashing a lot who are they and why are they saying it?
Are they an MS employee that loves MS and the XB1? Probably not. Are they a disgruntled MS employee, someone who wants to see the XB1 fail, a guy at a developer competing with the XB1, someone who gets a kick out of seeing the information they shared go viral? Probably something along those lines.
Any time anyone shared secret info with Mort they must be thinking about it going public and what that means, and must want it to go public. Maybe it started as a guy who knows some people in the industry who share tidbits, but at this point it has to be people using him to get across what they want.
Simply repeating information from anonymous sources is extremely prone to abuse. The guy who said that the XB1 was very unstable - what happened to him? Nothing. He got the message he wanted out there, and when it turned out to be false there were no repercussions.
Edit: A lot of what Mort says comes off to me as basically true, but worded more dramatically than is warranted to make fairly normal issues sound major. It's like how Kotaku contacts the 8 most disgruntled laid-off workers at a dev and prints their office gossip as some sort of expose, billing the sort of stuff you hear at literally every developer (the upper management is fickle and asks for irrelevant changes!) as serious issues.