Not sure what the proper origin of the debate on 10x was, and if it ever was talking about productivity. In my mind the point about the 10x developers had always been about the fact that some developers' VALUE (not productivity) is 10x. And in that sense it seems to me that the factor 10x is, if anything, an understatement.

A room full of 100 average physicists, or 1000 bad physicists, would never never have been able to make the contribution to physics that one Albert Einstein made.

And I think it's the same with developers. It's not rare to have a team of 10 developers with one individual whose creativity and problem solving ability means that the product that this team is building is better than any competitor's and that none of the problems that arise will stop the team's ultimate success. In this sense it might well be ONE engineer who is the catalyst for a chemical reaction that allows the other 9 to have an opportunity that sheer productivity can end up getting converted into value, the thought experiment being: If you take the team away from that guy, he could still build it by himself (but would take 10x as long, compared to how long it would take the team to do it). But if you take that guy out of the team, then the other 9 could expend infinite resources and would never get anywhere.