Everyone is making such a big deal about Meb not running and that the BAA is racist and what not. Meb wasn't offered a fair offer so he decided not to run, simple as that.
At this late in the game Brett probably got little or no appearance money from BAA. Brett just wants to make up for his poor Houston performance. People make it seem like BAA wouldn't let Meb run. That is not true, they just couldn't come to an agreement.
As for Nick he was coached by Greg all the way through Houston. When he said he wasn't doing Greg's specific marathon training leading into Houston it only meant that he was doing less mileage. He was still following Greg's training. Part of coaching is figuring out what each athlete needs to run their best race. That is going to be different from Brett to Nick.