B737-300 HAD AN UNCLR CLRNC AND CTLR DISINTEREST IN THE CLRNC QUESTION ON TAXI IN SFO.

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ON TAXI FROM MAINT TO GATE; CLRED VIA ZULU SIERRA; HOLD SHORT OF RWY 28R. I COMPLIED; BUT WHEN CLRED TO CONTINUE; WAS TOLD I SHOULD HAVE CONTINUED AROUND THE EXTENDED CTRLINE OF RWY 28R. THE COMMERCIAL ARPT PLATE XYZ PAGE AND THE TAXI MARKINGS SUGGEST THE INSTRUCTION 'ZULU SIERRA' CAN BE FOLLOWED BY XING RWY 28R OR BY GOING AROUND RWY 28R. I HAD POINTED THIS OUT 30 MINS EARLIER TO GND; BUT THEY WERE NOT CONCERNED. THEY WERE CONCERNED LATER BUT UNWILLING TO ADMIT THEIR INSTRUCTIONS WERE NOT PRECISE. SUPPLEMENTAL INFO FROM ACN 502737: WE WERE CLRED BY ZZZ GND CTL TO TAXI FROM THE MAINT TO GATE VIA ZULU; SIERRA; BRAVO 1; ALPHA; HOLD SHORT OF RWY 28R. AFTER TAXIING CLR OF THE MAINT W GATE WE UNDERSTOOD WE WERE ON TXWY Z BASED ON THE TXWY SIGNS. WE HELD SHORT OF THE N SIDE OF RWY 28R ON TXWY S AND WERE INSTRUCTED TO CROSS. ONCE WE WERE ON THE RWY; THE CTLR TOLD US HE WANTED US TO TAXI AROUND THE END OF RWY 28R ON TXWY Z AND TO CALL THE TWR ONCE WE WERE AT THE GATE. THE CAPT CALLED THE TWR SUPVR AND WAS TOLD WE WOULD HAVE HAD A RWY INCURSION IF NOT FOR THE ACTIONS OF ONE OF HIS CTLRS.