I found this in the fare rules: Does this not apply to standby?

10. PERMITTED COMBINATIONS
FOR ONE WAY FARES
ADD-ONS NOT PERMITTED.
FARES MAY BE COMBINED ON A HALF ROUND TRIP BASIS WITH ANY
FARE FOR ANY CARRIER IN ANY RULE AND TARIFF TO FORM
SINGLE/DOUBLE OPEN JAWS/2-COMPONENT ROUND TRIPS/MULTI-
COMPONENT CIRCLE TRIPS.
END-ON-END PERMITTED. VALIDATE ALL FARE COMPONENTS.
TRAVEL MUST BE VIA POINT OF COMBINATION.
NOTE - THE CITY PAIRS BELOW ARE CONSIDERED THE SAME POINT-
BWI-WAS FLL-MIA FLL-PBI MIA-PBI BUR-LAX BUR-ONT
BUR-SNA LAX-ONT LAX-SNA ONT-SNA OAK-SFO OAK-SJC
SFO-SJC EWR-HVN EWR-ISP EWR-NYC EWR-HPN HVN-ISP
HVN-NYC HVN-HPN ISP-NYC ISP-HPN NYC-HPN