If he just continues on and loses one or more stars then, no matter how public he is about the restaurant's change of direction, it will be widely regarded as a demotion. Opening a second, more informal eatery might not appeal to him for any number of valid reasons.
It seems reasonably clear that the ongoing cost in terms of anxiety and, to some extent, the freedom to change or loosen up things is simply not worth the accolade to him anymore. The article states: "because of the huge pressure of being judged on every dish he serves... and the anxiety over Michelin’s anonymous food judges, who could arrive at his restaurant at any moment... “You’re inspected two or three times a year, you never know when. Every meal that goes out could be inspected. That means that, every day, one of the 500 meals that leaves the kitchen could be judged. “Maybe I will be less famous but I accept that,” he said, adding that he would continue to cook excellent local produce “without wondering whether my creations will appeal to Michelin’s inspectors”."
So, he's quitting on his own terms. Assuming it's not a rash decision borne from burn-out or some temporary phase or state of mind then I think it's admirable.