I'm going to make a comment that may many may not like......
We greatly overthink "The Lore". We continually try to find real world meaning in it all and there basically is none. Since when has it all meant anything more than a simple statement. How many words or lore did they wrap around "Su birthday concert in Hiroshima", for instance.
In our current situation, all of this lore has two simple meanings that are actually separate from each other....
Chosen 7 and all the lore wrapped around it - Has nothing to do with what is happening on stage. Only related to the graphic novel. We know who they are. They are in the Distortion video.
"Darkside" and OTFGK who, when and where mumbo jumbo. That's their way of saying, "It's different" and "Yui's not here".
That's it. That's all of it. Nothing more.