DC10 AND B757 ASSIGNED PARALLEL VISUAL APCHS ON RWY 28L AND RWY 28R IN SFO. DC10 IS SLIGHTLY BEHIND B757; BUT HAS A HIGHER MINIMUM APCH SPD. SPACING IS SUCH THAT DC10 SLIDES SLIGHTLY AHEAD OF B757. B757 EXECUTES A GAR AT 500 FT.

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ON AN APCH TO SFO; WE WERE CLRED FOR A VISUAL TO RWY 28L AND A B757 WAS CLRED TO RWY 28R. ATC ASKED US TO KEEP VISUAL WITH THE B757 AND CONTACT TWR; WE WERE BOTH CLRED TO LAND AND JUST ABOUT SIDE-BY-SIDE. ON SHORT FINAL; WE WERE SLIGHTLY IN FRONT OF THE B757 AND THEY ASKED ABOUT WHETHER; SINCE WE HAD A VISUAL AND WERE INSTRUCTED TO KEEP VISUAL SEPARATION; WE SHOULD BE SLIGHTLY PASSING THEM ON SHORT FINAL. BOTTOM LINE WAS THAT THEY INITIATED A GAR. MY CONCERN IS; WAS IT OUR RESPONSIBILITY TO NOT PASS THEM; EVEN THOUGH WE WERE NOT GIVEN INSTRUCTIONS TO NOT PASS? ON THE CHARTED VISUAL INSTRUCTIONS IT NOTES TO KEEP A SLIGHT STAGGERED SEPARATION. WE WERE NOT CLRED FOR THE CHARTED VISUAL; SO DO THOSE NOTES APPLY? EVEN THOUGH THE B757 OPTED FOR A GAR; THERE APPEARED TO BE NOTHING UNSAFE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: CALLBACK CONFIRMED THE DISTR CAUSED BY THE WINGTIP-TO-WINGTIP OP DIVERTED THE FO AND SO'S ATTN OUTSIDE. THE CAPT WAS DISTR MAKING SURE HE DID NOT FLY R OF THE RWY 28L LOC. THE END RESULT WAS THE CREW FORGOT LNDG GEAR EXTENSION UNTIL WELL INSIDE THE OM. THEY ALSO MISSED SEVERAL ALT CALLOUTS AND HAD A DELAYED CHKLIST.