No, no. I don't think you get it. a .000112% (miswrote it the second time) chance means that population and future births have already been taken into account (as stated in obituary by the statement "[this statistic produced] by objective measures too complex to detail in this obituary". It's an all inclusive statistic. What you are thinking of, would be something along the lines of "only .000122 of every 100 children will ever 'lead civilization into a future of equivalent quality.'" Such a statistic is at its core completely different from the one outlined in the obituary, get it?
I understand what you are saying about it. I find it highly unlikely that that view point is realstic due to the fact that so many extraordinary individuals live in a region (The Southwest) that can't have more than 1.5 million people. The Tandis, Couriers, Vault Dwellers, Kimballs, Caesers, Grahams, Lanius', House's, Hanlons's of the world that arguabiliy meet or beat House's accomplishments given their circumstances. That said there are only two things
A. It's from a view of 1 out of every Million will be of the same level or greater than House
B. It's simply wrong due to the bias of House and lies in the obituary (How he stopped all 77 warheads when he only stopped 68) and the probablity he massively increased the amount by which he's great in comparison to others.