I generally agree that we shouldn't armchair diagnose people, especially not for gossip's sake. But in this case Bryan is actively promoting a lifestyle which looks symptomatic of a disorder, so it's probably in the public interest to point that out.
The post author did so in a thoughtful and respectful manner.
Exhibiting symptoms of a disorder is not the same as having a disorder which is why it's irresponsible and inappropriate to diagnose people based on their social media.
Bryan clearly is not anorexic because he gained a bunch of weight/fat when his doctor told him he was at a dangerous weight. Someone suffering from anorexia is not going to increase their body fat by 5-10% on their doctors recommendation.