Is Menma's comment on Tenten being not the Tenten he knows being a hint that he knows this isn't her world? In a way, similar to how the "Road To Ninja" Sakura was somehow able to enter the real world temporarily?
I think he was but that it was totally focused toward manipulating things to get her to stay in the illusion. I think if she had continued to reject the simulation it would have just reset itself and tried something different. In contrast the limited Tsukuyomi that created alternate Sakura and evil Menma were also self aware but because it was incomplete it actually allowed them to act against their programing. It's like their incomplete programming in the later case let them do more than they should have. Its the only way that makes any sense to me.