There's nothing baked in stopping moons from being freed from their planets other than code for that hasn't been written yet. Indeed its the general consensus among the community that creating more addresses by liberating moons would be what is done if the ~4 billion limit were ever reached.
There's ordinary mathematical reasons for the 4 billion limit - it makes the address space 32 bits. I've never met anybody working on Urbit that believes the notion you're putting forth.
OK - could the folks working on Urbit update that page or indicate that it doesn't reflect the current project's plans/beliefs, then? A "Common objections to Urbit" page that says "We would and easily could add more than four billion planet-like entities if the need came" would be far more convincing to objectors than "Actually, there aren't four billion people in the world deserving of our project's goals."
(I realize the document is from 2016 and written by someone no longer associated with the project, so maybe a disclaimer at the top linking to an entirely new version of the document would work, or something.)
There's ordinary mathematical reasons for the 4 billion limit - it makes the address space 32 bits. I've never met anybody working on Urbit that believes the notion you're putting forth.