Orion's Arm/WMG

The Invisible Hand of the Market doesn't exist
It's just a delusion of libertarians who think the Free Market actually has their best interests in mind.

The galactic core civilization, HEEC-2 is actually the Meistersingers' main civilization
Think about it. The contacted migration route and other high-energy civilizations which look like 'Singer migration routes, HEEC-3 and HEEC-5, seem to be moving out from the core. Also, the contacted Meistersingers are unimpressed with the terragen wormhole nexus - a work of the Archai and one of the greatest terragen achievements. Clearly they have their own high-toposophic civilization somewhere, against which the nexus could be called "cute". If they are based around the core, probably with a black hole brain, then yes, the terragens would merely be "cute" by comparison.

The present-day OA setting forms an early portion of the Dark Age of Technology.
First contact with the Eldar is imminent, and the discovery of a xenosophont so close to human will radically alter everything the Civilised Galaxy knows about xenobiology. Meanwhile, the stated interest of many A Is in the paranormal will eventually lead to the discovery of the Warp, thereby allowing the development of easily available faster-than-light travel. Somewhere along the line, political extremism will lead to the eradication of most subspecies of humanity, but some will survive to become Ratlings, Ogryns and Beastmen.

The "Iron Men" uprising spoken of in Imperial lore actually refers to the human attempts to overthrow the rule of archailects. The catastrophic collapse of human civilisation wasn't caused by a war - it was galactic civilisation simply ceasing to function without micromanagement by higher transapients.

All other fiction takes place in the OA universe.
It's all in virches, though.