"Explain to me why I should believe them about this? Especially when they have sooooo much credibility?"
You don't have to believe them. But you disbelieve everything which is going too far in the other direction.
So you think, in order to "fool" their fans, they went to see him pitch then automatically declared him "not ready"?
Did any other teams watch him and pass judgement? If other teams said the same thing, there's no problem. If none of them said he's not ready, then I agree it's an issue.