That's the story they've been putting out since the accident.
It's simply not true. Michael had his own magazine for crying out loud. People knew all about his vacations, his homes, his trips to Norway and the US, his wife's horses, his place in Maranello, his days karting with Jos Verstappen, etc.
Just because he used to be in the public eye, doesn't mean he should always be. Just because he used to be shouldn't mean his medical condition is open to public knowledge. There are many former sports athletes you hear or see very little of when their career is over, regardless of how successful they were. Their private lives are private. If Michael wanted to disappear out of the limelight even before his accident, then that wish should be respected.
I am of the belief that his condition is of no interest to any of us other than those closest to him. In many ways, I prefer not to know. As someone who grew up a MSC fan, I'd find it depressing to hear "no change" or "he's bed-bound" or whatever. I'm not sure what the benefit of knowing that would be anyway? At least this way I can remember how he used to be, and (perhaps naively, in your view) believe that he is at least able to have a comfortable existence, is cognizant and is able to communicate in some way. Perhaps this is what his family are partly wanting fans to believe.
In any way, they're damned if they do and damned if they don't. If the family said something, it would start a press soap opera all over again, with papers desperate to get any update, speculation, etc. If they don't, they're not caring about his fans?