I'm thinking they're waiting on the results of Tulo's appointment so they know if they should add him to the 60-day or 10-day. They probably prefer not to remove someone from the 40-man if he's going to the 60-day.
I don't have any idea what is going on there. They could have cut Dickerson, and come out $4+M ahead of where they are now. Surely Tristan Gray isn't worth that much to them.