My reasoning for it is that you can have multiple trains on the same track without one going back and forth on the same bit of track. It should dramatically increase capacity with a twin track system.
I'm not actually sure what the height of the current hub is and what the average height of monorail track is. Rising it above the hub will allow for all the walkways to remain.
It would be a pretty great view when you arrive too.
You've got Hulk, JP, Hogwarts, Dragon Challenge, Rockit, Studios entrance, Transformers, Diagon, MIB, Nintendo if it gets put into Kidzone and Hard Rock Hotel.