One of those center squares is taken up in 0.9.1.2, the boss added with that version. The other two are not added yet. I'm assuming the squares on the lower right are also for future enemies, like the Casino Bunnies.
The Duo Fight with the mermaids might be the only one working properly as a refight, as it's a known bug that visiting the recollection room will unlock all of the fights. Finding that fight shouldn't be hard, it is in the main tower.