Cheeks is just experimenting and seeing what he can get away with. This is the time to do this, when it doesn't count against your team.
The Sixers are a little thin at the power forward spot. Once they get past Brand, all we have is Evans and Reggie is not a guy you want taking shots in a game. If Theo can give us support at Center than Speights can play backup PF and we get a lot stronger with the 2nd unit. Cheeks put a group on the floor that he'd never have to actually use in a game.
It's unfortunate, but so far, Cheeks hasn't been able to get a good look at Ivey and Rush. It isn't certain that they'll both stay active with the team. They will both have to beat out Willie Green to stick and it doesn't appear either is good enough.
Once the season starts, two of five players will be on the court at all times, Miller, Iguodala, Brand, Young and Williams.