SS, I don't know WHAT it is. My H stored his TV box in our basement, left all his fall clothes and several shoes, diplomas hung on the walls of his home office, and lets himself in to borrow the drill and use my Command adhesives when he feels the need. He left some of his toiletries on the bathroom counter, too!
He also asked me to take delivery of the sofa he bought for the apartment. (!!) I told him THEN that if we were going to be separated then we had to be separate. That was just too big a request to accommodate. I did help assemble the stupid thing because I really needed him to take the kids the following weekend and I was afraid he wouldn't if he didn't have the apartment set up. That actually ended up being a productive activity.
My MC/IC was astounded that he does't have space set up for the kids (the boys sleep in his bed when they stay, my D on a futon in his home office, and he sleeps on the couch), nor does he have ANY toys at his house for them except the Skylanders that go to the xBox. (D doesn't play with those). IC thinks he hasn't got his head around this being a permanent situation. I'm just letting it go. It's not like I want it to be more permanent.
It may or may not be cake-eating, but I think whether or not it is depends on you and how you respond to it. If you're just letting it wash over you and not being emotionally invested in what he's doing then maybe it isn't, and if it gets your hopes up and keeps you from detaching then maybe it should stop.
Me42, H40 D12, S8, S7 A revealed: 7/13 Sep 4/14; Agreed to D 1/15