I am no expert here but you can't ignore the fact that Hall was running 2:06 after training at altitude and 2:04* after training at altitude. You can also not ignore that virtually all Kenyans train at altitude.
Two questions arise here:
1. How big is the difference in the Marathon with vs. without alt training? My guess is 3 minutes.
2. Is he on something (CERA?) that makes altitude training obsolete?