But if Jaylen is already disgruntled and wants out, why wouldn't he be happy to hear his name in a big trade?
Well, I think you added a step. A guy can be disgruntled, but not want out.
To use an analogy... A guy is a little unhappy in his relationship with his girlfriend. He feels like he's not getting enough attention, she's blowing him off, etc. But, he wants to work on some things and build on the good aspects of the relationship, while trying to find some compromises in other areas.
If he then hears his girlfriend has been giving her number out to single guys, he's probably not going to be happy. He'll just be more disgruntled, until he breaks it off.