Because there is no RNAV Approach for RWY13L.
Because in the US they call it a GPS approach?
The caveat here is that we are used to a continuous descent. We do that all the time. Here it isn't. If you cross DMHYL at 800' you're about 3.5 NM out so about 300' low. If you continue descent you're in for a surprise. I guess they discovered that the hard way. Better to find out in the sim; as a regular to JFK, we do.
A lot of fun, but a challenging approach, already harder in a heavy then a 73, must be twice as hard after a long haul from DXB.