Oh don't get me started on that! ''We swear to you guys, it's not purgatory!'' We were conned, people... CONNED I TELL YOU!
No, if i recall correctly, the writers kept saying that the ISLAND is not purgatory, and the ISLAND is not heaven or hell. They did not say anything to my knowledge about the Alt. Reality being purgatory. This is why(to me at least) the revelation about the alt reality was a complete shock. When the writers said these things about the island, i totally dismissed the possibility of the alt reality being purgatory.