I'm not sure why they joined them either.
had:
jfk-scl
scl-lax
lax-jfk
on one PNR (booked via AA rtw desk)
jfk-syd
syd-cns
cns-syd
syd-hba
on 2nd PNR (booked via BA rtw desk).
When I reissued the ticket (via AA) they made me pick dates instead of open for my original open-dated segments, these they put into the first PNR, but for some reason they also merged the 2nd PNR into the first.. if they had done it the other way around (or just left well enough alone) I might have been OK (or I might have lost the LanChile flights in that case, who knows).
[This message has been edited by hauteboy (edited Dec 18, 2003).]