They had already been proven wrong when he breathed on his own for several days longer than they promised he would.
Yep. Doctors should be able to nail the prognosis of a disease of unknown origin. Diseases of known origin progress on an entirely predictable path with no variation among individuals.
For example, we know Stephen Hawking did not actually have ALS because he outlived his prognosis by decades. He got a talking wheelchair because he thought it was cool.