Think about it. If this was true, you'd see much bigger stars make a fuss when they're left out of training. Or you'd see clubs making a fuss when players SKIP official trainings to force a transfer. If that "access to first team training" is what people think it is, it would go both ways.
Fact is, it just doesn't make sense from a contract law perspective that there would be any clause or requirement in a contract that GUARANTEES a player access to first team training and being on the squad. How could any club enforce that? How could you bench a player for bad performance? These are regular occurence all throughout world football and Bonucci's lawteam is the first to crack the code? Much more likely there is a clause in the contract that a player has access to training facilities because physical training is such an important part of their job. And nobody has told Bonucci he can't show up to the gym and train by himself to stay in shape. And to add to that, he has refused transfers away from the club as well after being told he had no place on the squad. Clown show moment from him.
Much more likely this is just bullshit atttempt on his part to try and force a bit more money out of the club to cancel his contract. And sad to see his disrespect the club, regardless of how you feel about our management, in such a public and embarrassing way. Embarrassing for him and the club.