Hardly speculation.To run an 800m in 1.41.73 takes, not just good basic speed, but incredible endurance.You cannot run a fast 800m unless you've developed your stamina to the maximum.The greater your endurance the longer you can sustain your pace.
Seb did this through intelligent training in an era without EPO.Just because someone doesn't run a particular distance, doesn't mean they can't.One other point that shouldn't need to be made is:
Steve Ovett ran a world record 2miles.Since Seb was equal to Ovett in ability and 2stones lighter, it's obvious he could run as fast or faster over longer distances.You simply cannot ignore the relationship between speed and stamina.
I've given loads of examples but some of you still don't get it.