Whoa, you guys, the person who wrote that didn't work as a writer, didn't work for LOST (only for ABC), and posted afterwards that he was sorry if his post got picked up as inside information. It was his own spec, as someone who worked as a gofer or something totally on the outside of the process. Now breathe.
It is the task of any writer to make the ending feel as if it flowed from the beginning. These writers took a rather easy route. They decided to mirror the opening. They preserved Vincent's availability so they could have him in the final scene. They got Season One actors to come back for cameos (even though poor Boone was left all alone at the end with a church full of couples).
This is a writing technique. Fox explained exactly what he knew. He knew he would die and the final image would be his eye closing. He did not know if his character would find redemption, but hoped so.
Do you realize how easy it is, when you've made a pilot with a distinct opening shot, to decide that will it be cool to close whatever you do -- which at the time they thought would be 12 episodes -- with the counterpoint to that image?
Open eye ..... Shut eye.
It was effective. All I'm saying is, there is no overarching concept or mythology that must be in play to make that particular creative decision in advance.
I don't think it is necessary to have it all planned out from the beginning, and I'm not even sure why it matters to so many people. The reason I resist it, is that if people look at early themes introduced into the show that got dropped, it makes more sense, Occam's Razor, to attribute that to writers finding their way. If people insist that it was all planned, it becomes necessary to make big stretches and even concoct unlikely theories, fill in the holes with fan spec, and so forth. Duct tape.
In any case, the easiest parts of a story to write are the very beginning and the very end. The hard part is writing a coherent, consistent and high quality middle to the piece.