This really isn't that insane. I ran a spring marathon (I'm much slower than Sifan Hassan). I ran two track meets in the lead up to the marathon as workouts. I did the 3000/1500 double in the track meets. It was useful for the marathon and I ran a big PR. There were other spring marathoners doing the same thing in those races. The only difference with what Hassan is doing: she has a decent chance to win all three rather than run in the marathoner pack 150m behind the leaders.
