Not going to dispute anything you say here...but I will present another view....
If you are a tech geek and you had a chance to sit down with Steve jobs or if you aspire to be president one day and you got the chance to visit the president for a couple days in the white house...or if you wanted to be an actor and you got a chance to visit Leonardo dicaprio (sp)....or you were an aspiring singer and you got to spend time with Barry Gordy at Motown....would there be anything that would keep you from doing that?
Personally, it'd have to be pretty serious for me to not take advantage of an opportunity to not want to hang out with and maybe learn from someone considered to be among the best in my field.
Manziel and the manning passing camp. You love playing qb...eat, breathe, live football. But you get sick, of drunk, or over sleep, or whatever and miss that chance?
I don't know manziels soul, but surely you can understand why some people would have some questions about him in this area.
Maybe he found out Peyton wasn't going to be there.