Smg1991 you beat me to it. MJF has a new TV show and it is based on HIS LIFE. He plays a TV anchorman struggling with Parkinson's.
I'm sure his network wants him on Letterman to plug the show. He might throw in some comments about how there are promising therapies or something, but it's silly to think AMBS is the reason for his appearance. He'd be going on the Today show or something like that, if he were announcing a breakthrough Parkinson's treatment.