Haymon don't want Hearn calling all the shots and manoeuvring the career of his HW champ for the sake of making another million nobody involved really needs. Makes sense to me.
Then why did Haymon do just that when he sold Martin's IBF belt for a fraction of what Hearn is offering for Wilder's belt? Not necessarily disagreeing with you as what you said makes sense but clearly there is more to this as Haymon has done the very thing you said he wouldn't do.