Level 0 is gigantic, we know that. The chance of meeting another human is infinitesmal, but what about corpses?
Humans can last 3 days in Level 0 without supplies (Assuming they were not dehydrated or sleep deprived before going in and were not attacked by an entity), and not many people ever leave. We know that there are 6-15 trillion of people who exist inside of the Backrooms, and that the timeframe of it's existence spans at least 140 years.
I'd estimate that 4 trillion or so people have died in Level 0 (idk backrooms scaling is hard).
With the original post claiming 600 million square miles, mathematically this means 6666 or so bodies per square mile, so the carpet would just be covered in human bones.
Assuming that the M.E.G page (On this wiki) was written between 1885 and 1900 and the M.E.G were among the first people to noclip, that explains the page not mentioning this.
The M.E.G could not colonize Level 0, nor could they recruit from there, so entering or documenting it was an expense of resources not necessarily furthering their interests. That would mean that after the initial testing and documentation in that 15 year time frame, they chose to abandon Level 0.
Kind of a pointless theory, but I feel like it makes sense.