In the Old verses of Arceus legend, they literally reuse, line by line in japanese, the verses from the leaked development document "pmyth5.2 AUSU."

And in every instance that the true names of the Gods, Aus, Ea, and Ia are used, they are replaced with 3 Question marks "???" as if to directly call out the names of the kotoamatsukami that are behind the 3 pokemon avatars of Arceus, Palkia, and Dialga.

This also corresponds with "pmyth5.2 AUSU" explaining the mystery of the Flame Plate and the Earth Plate. That in the beginning, the cosmic egg burst open with Arceus, and the eggshell became giants of every element that attacked Arceus. (Earth Plate)

Arceus slayed the giants until they were nothing more than the plates (Flame Plate)

Finally, PL Arceus reaffirms the Sinjoh Sigil as canon, of which, only "PMyth5.2 AUSU" explains correctly with designations for Dragonite(winds creates by Rayquaza), Gyarados(waves created by Kyogre), and Tyranitar (quakes created by Groudon).

PL: Arceus affirms that the development document "PMyth5.2 AUSU" is the one that is used internally to align the in game content.