No alt reality.
I have just read a theory by emzi that made something in my head go click. It was about Jacks appendix scar and Jughead. What I propose is that the alt and possibly the on island timeline are not real. Or one is and the other isn’t. Smokie scanned all our losties and is using all their memories to create an alt where they all get what they want out of life.
I mean I know they were all intertwined in some way but did Keamy and Sayid meeting not seem just a little bit of a stretch.
Maybe this is why there has been bleeding between the two realities. Either there are two realities where the losties are in stasis enjoying a fantasy life In one and a war in the other or one is an almost perfect life and the other is war. Either way there are two versions of everyone out there.
Have fun tearing this apart.