no, I am saying a drop/grav step after the split is faster. In your second example you are including the pivot step into the split - which is what I described earlier and user92 was describing as difficult/dangerous for him to try. Most players don't/can't land their split step with the pivot incorporated, so for them a jab step may be the most efficient. If you can include the pivot into your split step, then a drop/gravity step followed by a crossover is without doubt the most efficient.
In your Murray video the first few his is worning wide, byt there is no split and then he is working on footwork for return of serve, which is different - Jez likes the powerstep for the return of serve as a way of quickly re-establishing balance and iding recovery.