I was in the Los Angeles area last month and they use X Y Z also over there to differentiate between procedures that have you fly to the same runway using the same IFR approach (be it ILS, VOR, VOR/DME or GPS) but yet are different enough to justify a completely separate chart.
I flew out of Camarillo KCMA, and there are two GPS runway 26 approaches, Yankee and Zulu. Yankee is slightly offset to the north of the runway centerline, while Zulu is pretty much aligned with the centerline but interferes with other airspace in the area (or so I was told). Yankee is then the preferred GPS approach into runway 26 at KCMA.
Ciao, Luca