Hm, i don't know about that: There does seem to be distinguished differences between the Slimes' ectoplasmic constitutions and the Junimos' spectral morphologies, and there are clear taxonomic differences between them. Wherever the aforementioned journals cane from, they may have been the rantings of a madman as opposed to genuine research;
However:
Recently we managed to get the bus back to Calico Desert up and running again, and the Calico has proven to be an exciting opportunity for archeology: For one, there are untouched(!) fossils simply bleaching in the desert sun(!), and study shows that the salt flats of the Calico were likely a flood basin ages before they were a roaming ground for what appears to be dinosaurs; considering that the dinosaurs went extinct in the Xichulub Meteor Extinction sixty-five million (65,000,000) years ago, that would make some of the ruins here exceedingly ancient!
Additionally, we found another key on the bottom floor of the mines, one hundred and twenty (120)(!) stories(!) below the surface, and somehow, the Skull Key fit perfectly into a lock built into a door in a cave in the middle of the flood basin(!): Inside we found clear evidence of humanoid occupation, up to and including preserved undead humanoids; we attempted to speak peace to them, but the shambling horrors attacked us relentlessly; similar adventurers had encountered similar monstrosities and lived to write about it, and advice to use small explosive ordinances against their unrelenting remains proved effective;
The real gold, however, came not just from the incredibly mineral-rich deposits within the caves, but on the cave walls themselves: Whoever built the tomb-like enclosures recorded things on the walls, and the writings seem to consist of an eight (8)-bit language, consisting of two-by-two (2x2) square characters written in light or dark bits; these caves were exceedingly dangerous, but there seems to be clear evidence that intelligent life once occupied the Calico Desert.