I'd not say hes being unprofessional, it sounded like genuine illness on Monday as he was back at training on Tuesday.
The rumors are that hes told the club he wants to pursue a move (likely because he'll be on double+ wages rather than the "playing where his "heroes" played" bollocks), if this is true, he probably is anxious that it won't get done, so totally accept why he is missing Atalanta game. It also suggests to me that the clubs are close enough to agree a fee before the transfer window ends and it would be detrimental to play him when we need to see other defensive partnerships before Wolves.
As for the agent rumors, of course his agent is plugging for a move, if it was upto agents, they would move their clients to different clubs every summer so they get a huge chunk more cash every year. Agents will never advise their client to stay put when they can make bank.
I'd have more respect for him if he actually put in a proper transfer request so he'd waive any loyalty bonus meaning we could accept a lower fee from Man U, but it doesn't seem to me that hes that desperate to move or he thinks he can hold out for both to happen.