MULTIPLE RWY OP PARALLEL RWYS. VISUAL APCHS. ACR X MADE GAR AS ACR Y THOUGHT TO BE ON WRONG RWY.

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ACR X CLRED FOR THE TIP TOE VISUAL APCH TO RWY 28L AT SFO; WITH AN ACR Y ON THE PARALLEL TO RWY 28R IN SIGHT; SLIGHTLY AHEAD. DUE TO SPD ASSIGNMENTS AND SEQUENCING; IT RESULTED IN A WINGTIP APCH. WE STAYED DELIBERATELY L OF CTRLINE AS THE OTHER ACFT SEEMED TO BE LINING UP FOR RWY 28L. AT APPROX 500 FT IT STILL APPEARED THAT HE WAS INTENT ON RWY 28L AND WE COULD NOT QUERY HIM NOR TWR DUE TO FREQ CONGESTION. WE ELECTED TO GAR AS WE WOULD SOON BE OUT OF POS FOR A NORMAL STABILIZED APCH AND LNDG. TWR LATER (ON THE GAR) TOLD US HE WAS LNDG RWY 28R; BUT WE HAVE NO IDEA IF THAT MEANT HE COULD SEE (RADAR) THE ACFT ON CTRLINE OR IF HE WAS MERELY 'CLRED FOR THE APCH.' WOULD LIKE TO KNOW THE EXTENT OF TRACKING FACILITIES (IF ANY). BOTH TWR; AND LATER APCH; ASKED US THE REASON FOR THE GAR. WITH ONLY THE NAV AND STROBE LIGHTS AND NO MOON OVER THE WATER IT WAS VERY TOUGH TO ASCERTAIN DISTANCE. COULD ONLY SEE APPARENT CLOSURE AND FEELING OF EXTREME DISCOMFORT. SUPPLEMENTAL INFORMATION FROM ACN 261032: ACR X CLRED FOR NIGHT TIP TOE VISUAL TO RWY 28L AT SFO; WHEN STILL S OF RWY 28L LOC. SEQUENCING AND SPD ASSIGNMENTS RESULTED IN TRYING TO GET ON RWY 28L CTRLINE ALONG SIDE ANOTHER ACFT; ACR Y. VISUAL CUES AT NIGHT WERE NOT SUFFICIENT FOR ME TO BE SURE OTHER ACFT WAS ON THE RWY 28R LOC AS ASSIGNED. FO COULDN'T TELL; EITHER. FO ASKED TWR ONCE ABOUT SIT; TWR SAID SOMETHING LIKE 'HE'S ON RWY 28R' WHICH DOESN'T REALLY TELL US IF HE IS IN FACT ON THE RWY 28R CTRLINE; OR JUST SUPPOSED TO BE. FO TRIED TO ASK AGAIN BUT FREQ WAS TOO CONGESTED. WE GOT DOWN TO ABOUT 500 FT; AT WHICH TIME IT STILL APPEARED TO FO AND ME THAT MOVING OVER TO THE RWY 28L CTRLINE WOULD PRODUCE A COLLISION HAZARD. FO ADVISED A GAR; AND I AGREED. GAR WAS UNEVENTFUL. SUGGESTION: HAVE APCH AVOID FORMATION APCHS AT NIGHT; AND IF THEY ARE ASKED IF OTHER ACFT IS ON HIS CTRLINE; MAKE IT CLR WHETHER THEY ARE TELLING US THAT HE IS (RADAR) VERIFIED ON TRACK; OR MERELY SUPPOSED TO BE ON TRACK.