AN ACR CREW DSNDS BELOW ASSIGNED ALT WHEN FLYING THE LUXOR ONE ARR TO LAS; NV; WITHOUT A 'VIA' CLRNC.

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I WAS THE FO ON THIS FLT ACTING AS THE PF. THE CAPT WAS THE PNF. WE WERE INBOUND TO LAS AND CLRED FOR THE 'LUXOR ONE' ARR WHILE OVERHEAD MILFORD (MLF) VOR. ZSE CLRED US TO CROSS 'LUXOR' AT 12000 FT AND 250 KTS. WE COMPLIED WITH THIS AND UPON PASSING LUXOR AT 12000 FT AND 250 KTS; WE DSNDED FURTHER SO AS TO CROSS MIRAJ 'AT OR ABOVE 10000 FT AT 210 KTS;' FOR RWY 25L AS DEPICTED ON THE LUXOR ARR. MIRAJ IS ONLY 10 DME BEYOND LUXOR. WHILE PASSING THROUGH 11500 FT; LAS APCH ASKED US IF WE WERE CLRED BELOW 12000 FT. WE REPLIED THAT WE WERE CLRED FOR THE 'LUXOR ONE' ARR AND TO CROSS LUXOR AT 12000 FT AND 250 KTS. THE AIRSPDS AND ALTS AT LUXOR AND MIRAJ ARE NOT DEPICTED AS 'EXPECTED' RESTRS SO WE TREATED THEM AS MANDATORY ALTS AND AIRSPDS. IT APPEARS THAT THE LAS APCH CTLR TREATS THESE XING RESTRS AS 'EXPECTED' ALTS AND AIRSPDS. WE INTERPRETED THESE AS HARD ALTS AND AIRSPDS. ALSO; UPON REACHING MIRAJ; WE ASKED THE CTLR IF SHE WANTED US TO DEPART ON A 205 DEG HDG AS DEPICTED. SHE DID NOT WANT US TO FLY THE DEPICTED HEADING AND GAVE US AN ALTERNATE HEADING AT THAT TIME. WE ARE STILL NOT SURE HOW THE CTLRS WANT US TO FLY THIS ARR WHEN LNDG RWY 25L. WE WILL HAVE TO ASK PRIOR TO ANY ALT; AIRSPD; AND HEADING CHANGE THAT IS DEPICTED ON THE CHART. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAID THAT THE ARR WAS DISCUSSED IN DETAIL PRIOR TO HAVING IT ISSUED SINCE THERE WAS A LINE CHK IN PROGRESS. THEY WERE NOT ISSUED A 'DSND VIA' CLRNC SO THEIR ERROR WAS REALIZED AS THEY DEBRIEFED THE SIT AFTER THE FACT.