While I agree that there are quite a few things pointing away from it, I personally wouldn't go so far as to say there's absolutely nothing pointing to it: How about the sound of the Ajira jet, for one? It's the very last thing Jack sees and hears as he dies. The sound it makes as it passes overhead is the exact same sound used this season to introduce all of the sideways-verse segments. To me, that could be interpreted as a hint that all of the sideways-verse segments spring from Jack's dying vision. If not, why use that particular sound to preceed the flash-sidewayses? I can understand why the standard flashback "whoosh" wouldn't be used. (Was there a separate sound for the flash forwards, or was it the same whoosh?) But why the exact same Ajira noise Jack hears as he's dying? In hindsight, it would have been cool if each flash sideways had been preceeded by a whoosh made up of the sounds occuring during that character's death. For example, Sun and Jin's flash sideways could have started with the sound of flooding water. Sayid's with a whooshing explosion sound, etc. There's also the fact that the people in the church were Jack-centric (for lack of a better way to explain it). Why the pairing of Shannon and Sayid, for example, when it would have made more sense for it to be Sayid and Nadia? Arguably, it could be because Jack is more familiar with Shannon/Sayid than Sayid/Nadia. Not conclusive, but not "absolutely nothing," either. For me, it lends enough ambiguity to open the door to consider the possibility of there being an alternate interpretation. Like I said, though, ultimately I've come around to agree with you (and the majority). EDITED TO ADD: It's also possible to consider that while the flash sideways in the finale was Jack's dying vision/entry to purgatory, the other flash sidewayses throughout the season were not Jack's, they were those of the respective focus characters. I'm smeeking myself so I'll stop now.