Here's the relevant excerpt:
It all starts many years ago, when R&D was working on the set called Tempest. This story is about Maro and two young interns whose names are lost to time. Most people don't know this, but Maro wasn't actually hired as a designer but rather as a developer. He was eager, though, to prove that he could design, so he got Richard Garfield to agree to work with him on a new set. That was enough to allow the head designer at the time, a man named Joel Mick, to give him a shot leading a design."
"His first time designing was leading a set? That doesn't sound very plausible."
"Let me tell my story and then you can decide for yourself whether it's true or not. Anyway, there was a lot of pressure on Maro to deliver an exciting design, so he decided to push the boundaries. He made a new mechanic that allowed you to choose to start with the card in your opening hand. If you chose to do so, you had to begin with one card fewer."
"Just one card fewer? That's all? There wasn't a life loss or something?"
"The cards were weaker than normal, so you were opting to start with cards that were of a lower power level. Maro was excited by this idea. Everyone gets frustrated when they can't get the card they need. What if you had the ability to guarantee that you could have the card you wanted in your opening hand? But it was a bit of a crazy idea, so Maro knew it needed to be playtested. Luckily, Magic R&D had two young interns who were available for playtesting. He asked them to play in a room with a one-way mirror so he could secretly observe. The playtesting went on all night and Maro had had a long day, so several hours in, he fell asleep."
"What happened next?"
"Early the next morning, Maro awoke to see a message written in lipstick on the mirror, reversed so he could easily read it. It read: 'DECK VARIANCE IS THE LIFEBLOOD OF THE GAME AND UNDERCUTTING IT WITH THIS MECHANIC HAS LED TO THE MOST UNFUN PLAYTEST GAMES WE HAVE EVER PLAYED. IF THIS IS THE FUTURE OF MAGIC DESIGN, WE WANT NOTHING TO DO WITH IT.' The interns were gone and haven't ever been seen since. Maro took the new mechanic out of the file and never talked about it again."
So these young interns who have spent their entire lives studying, applying, working part-time jobs, taking loans, and navigating the waters of internship landed a dream job that requires testing games of magic for research and development. They were so offended by a game mechanic under development that they threw away their careers just after dramatically writing a detailed message with lipstick on a two-way mirror?
Rosewater's credibility just went to zero in my book.