MULTIPLE RWY OP PARALLEL RWYS VISUAL APCHS ACR Y HAD NMAC WITH ACR X. SEE AND AVOID CONCEPT.

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ACR X MAKING A VISUAL APCH TO RWY 28R. TWR CLRED US TO LAND. A BIZJET IN FRONT OF US WAS ALSO CLRED TO LAND ON RWY 28R. SPACING BTWN ACFT HAD REDUCED TO A POINT THAT TWR; IN AN APPARENT EFFORT TO ACCOMMODATE BOTH ACFT; REQUESTED THE BIZJET TO SPEND MINIMUM TIME ON THE RWY AFTER LNDG AND OUR ACFT TO S-TURN TO THE R. BOTH ACFT FOLLOWED INSTRUCTIONS AND LNDGS WERE COMPLETED. A THIRD AIRPLANE; ACR Y; WAS NEARLY ABEAM US AND SLIGHTLY HIGHER CONDUCTING AN APCH TO THE PARALLEL RWY 28L. WE MAINTAINED VISUAL SEPARATION AS INSTRUCTED BY APCH CTL FROM APPROX 12 MI TO LNDG. DURING LNDG WE HEARD ACR Y CREW EXPRESS CONCERN TO TWR THAT S-TURNING ONE ACFT ON A PARALLEL APCH WITH ANOTHER WAS NOT A GOOD IDEA; AND THAT OUR ACFT HAD INITIATED A TURN INTO THEIR ACFT. THE TWR CTLR STATED THAT HE HAD SEEN OUR MANEUVER AND THAT WE HAD INITIATED A S-TURN TO THE R; AWAY FROM THEIR ACFT. WE DID NOT SEE THE SIT AS DESCRIBED BY THE OTHER CREW. IT WAS POSSIBLE THAT THEY DID NOT SEE OUR INITIAL TURN AWAY FROM RWY 28R CTRLINE AND FIRST SAW US WHEN WE TURNED BACK TOWARD THE RWY 28R CTRLINE TO REJOIN THE FINAL. AT ALL TIMES WE HAD VISUAL CONTACT WITH THE OTHER ACFT; AND AT NO TIME DID WE GO L OF RWY 28R CTRLINE. SUPPLEMENTAL INFO FROM ACN 252341: DURING THE COURSE OF A PUBLISHED VISUAL APCH TO RWY 28R AT SFO; THE TWR ASKED US TO MAKE AN S-TURN FOR SPACING ON AN LTT JET AHEAD. THIS TURN WAS EXECUTED JUST INSIDE THE BRIDGE TO THE R. AN ACR Y WAS IN VISUAL CONTACT ABOVE US FOR THE L RWY. AT THE COMPLETION OF THE TURN HE WAS ABOVE AND SLIGHTLY AHEAD OF US. HE WAS IN SIGHT THROUGHOUT THE MANEUVER. THE ACR Y FLT MADE A COMMENT AFTER LNDG TO THE TWR REGARDING THEIR REQUEST FOR US TO MAKE AN S-TURN ON A PARALLEL APCH. THE S-TURN AND LNDG WERE UNEVENTFUL FROM OUR STANDPOINT. SUPPLEMENTAL INFO FROM ACN 252063: AT APPROX 3 MI OUT THE SFO TWR TOLD ACR X N THE R TO BEGIN S-TURNS TO INCREASE SEPARATION. AT APPROX 700 FT MSL (1 MI OUT) I WAS AHEAD OF THE R RWY TFC SO THAT HE WAS IN MY BLIND SPOT (BEHIND AND TO THE R). MY FO LITERALLY SCREAMED AS THE R RWY TFC APPEARED TO ALMOST COLLIDE WITH US AS HE WAS TURNING BACK TO RETURN TO RWY ALIGNMENT. THE SEPARATION ON A SIDE-BY-SIDE 'FORMATION' APCH IS MINIMAL AT BEST AND WITH THE OTHER ACFT TOLD TO MAKE S-TURNS; THE SEPARATION BECAME UNACCEPTABLE. ONCE INSIDE OF BRIDGE (6.0 DME) NO DEVS FROM COURSE SHOULD BE DIRECTED OR ALLOWED.