The 10x rule is that the best developers are 10x as productive as the worst 10 developers. That's all it says. So you can replace them with 10 worse developers, that's the whole frickin' point of the 10x rule.
I am not aware of any study that shows that arbitrarily complex tasks (a distributed operating system, an AI project such as Watson, an airplane fly-by-wire system...) can be completed solely by a sufficient number of bottom-of-the-barrel programmers. I don't recall any such claim in The Mythical Man-Month, but it has been a while since I read it - perhaps you could cite the chapter that references such a study, so I can look it up in my copy?