I agree with the premise, if he said "I was the first one to arrive at training, the last one to leave, my diet exceptional, total focus, and I wasn't getting a game so I had to go" - then everyone would be looking at his future performances and wondering if Mou missed a trick. Since he seems to have this rather 'half arsed' way of expressing his dedication to training, perhaps he has a "good enough" attitude, which is exactly what Mourinho wants to stamp out and if KDB is on his travels, well, there has to be a reason for it. Watching the Chelsea game yesterday, seeing the entire front line closing down constantly and as a team is what he demands and what he got. I'd love to be able to get that work ethic into the Arsenal forwards (everyone apart from Ozil seems to get it at the moment, but when one person stops the whole thing falls apart), but you don't get that magically on match day, you get it from training properly and with good attitude to give you the stamina and discipline to do it without the 'effort' on match day.
The funny thing is that Mourinho still wanted De Bruyne to stay so he could improve him. De Bruyne was the one adamant on a move. Can't blame him either. Also De Bruyne said that he had no problem with Mourinho so I think even he secretly knows that he needed to do a lot more work to get into the Chelsea team which he didn't do. I wish him well but if he wants to take himself to the next level, he needs to learn to embrace competition. At all his previous clubs, Genk and Bremen, he was the star so maybe now he couldn't handle being the small fish in the big pond