My theory:
The timeline goes RSE-DPP-RBY-HGSS
Then at this point, AZOTH comes into play as Arceus uses alchemy in the HGSS cutscene to create a new Earth inside of the Giratina egg. This new Earth is this one.
https://www.youtube.com/watch?v=GxC1kXm_AVsFRLG-GSC-ORAS-XY
Which is a dimension existing INSIDE of the Arceus egg Giratina.