I think that the large adjustments are flawed. If I recall correctly, the 800 is assumed to be just about a wash. Thus, over the next 700 meters adjusting from 3:34 to 3:18 is 10 seconds per lap as the comparative/differential effect. This is not even remotely reasonable.
It was a super race and the best 1500/mile of its time. But it is no better than a high 3:2x.
As for Beamon's leap, it is not so Beamonesque. It had, officially, a 2.0mps wind, the highest allowable for record purposes. However, accounts often indicate that the actual wind speed was even higher - we will never know for sure. You did not see any similar jumps because it started pouring ran right afterwards. If you look at the TJ you will find that the record was destroyed by several jumpers; not by as much, relatively, but a big breaking. He also got "all" of the board (and almost a little extra).