When a guy hits the pros, he ought to realize that he needs to work even harder if he wants to have success. I suppose that it is possible that Spencer, who has only known Wade Phillips as a DC and head coach, never really got that message. I don't know what the environment was like under WP; I wasn't at practice. But I do know that he defended the players in the pressers a lot. I don't think it's a stretch to say that Spencer has been coddled and entitled as a first round draft pick. In the past, he wasn't going to lose his starting position due to poor play.
Reading the article, I got the feeling that AS is waking up to the fact that he needs to work a lot harder. He talked about making mistakes in games despite knowing better, which is the kind of thing that happens when you don't prepare in the right way. He talked about lack of effort, which is often a sign of poor conditioning or lack of mental toughness.
Not coincidentally, those are the things that Garrett is stressing. Be prepared. Be well conditioned. Play with high effort.
I think it's worth noting that he didn't have a rap as a low motor guy before he came to the Cowboys. The little bit of research I did turned up phrases like "relentless," "plays hard," and "goes hard until the whistle blows."
I get the feeling that AS has had an intervention of sorts. I think it's a positive step that he recognizes that he wasn't putting in the work that he needed to. Too bad it didn't happen in 2007. Better late than never, though. Where he goes from here is up to him.