Idk, maybe this was disinformation, but i heard somewhere that back in early 2015 era of FNaTI, AnArt stated somewhere that FNaTI events can probably could take place in the same universe with original FNaF. So....do ya remember that in FNaF 2 Custom Night, we played as some guy named "Fritz Smith", and his surname is suspiciously same as Jake's surname, whose full name is "Jake Smith", so what if(at least before Oblitus Casa retconned everything.......FUK😡) it was implied that FNaTI Jake and FNaF 2 Fritz could be brothers(or at least just relatives)? Also, maybe that guy, calling Jake about his new job at Treasure Island, in secret ending of Blue Oddities can be also Fritz himself.

About MOTHER's hallucinations in this ending: well....do you remember that one very old 2016 Malrat's fan-made "full version"/revival of FNaTI 1.0-2.0, created after 3.0 cancellation? So....what if his old theory could become partically true, and Jake really was supposed to work on Treasure Island before FNaTI events? Maybe he could witnessed something horrible happened here, and could be connected to MOTHER in some way, so even after all this years he still remember this, and she is already messed with his mind, causing these dreams we see as Oddities series

P.S. Yeah, i KNOW that Oddities are confirmed to be non-canon, and lore of this ending was scrapped, but still