It's a literary methodology based on presumption of foreshadowing as a means of predicting the future. I would claim the largest assumption made is simply that Jan is an excellent storyteller, and that every breadcrumb he's left foreshadows and fits into a future plot.
If that holds, you can immediately make inferences like -- Rifts slot into the greater plot eventually. The Prophecies of Light and Dark are true. Erin's expressed doubts about the legitimacy of "the past" hold water. Yveltal is actually Melanie/MX-Xen's dad. That sort of thing.
Absent that, the entire analysis is bunk. Nothing more than a bunch of useless assumptions.
But, Jan's storytelling is exactly what inspired this. The crazy bastard put GOLD TEXT in his game, dammit. It was a magnet.
Re: the point. There is no point. Only a relentless obsession.
Well... Actually the point is to be able to say "I told you so" if all of this comes to pass. And I do think much of it will. Precisely, again, because Jan is an excellent storyteller, and there are only so many ways to fit all of the shards he's left us together into a whole.