No not injury related, illness and that was the distinction I kept making.
Ill not injured. illness should be private. It is a basic legal principle that an employer should not divulge any details.
Fair play though in Barton's defence I didn't spot that distinction either and reading back through I'm not sure it's a clear as you have made it until above.
Even in the circumstance of illness though the club can say something and a rough timeline. I've worked in many different environments where without disclosing the nature of the illness we needed to explain someone is absent and give a timeline even if undefined of absence. Again in fairness to Barton I don't get the impression the nature of the illness is relevant more the lack of communication and the vacuum that leaves.