I booked SFO-SEA-NRT, SFO-SEA in XN, SEA-NRT in I. I had a trivial schedule change (~5m) on SEA-NRT. Due to some weird system sync issues with NH where it still showed the change as unaccepted, a UA agent "forced" the acceptance through in fare class P (still XN for SFO-SEA). Do you think their system will let me SDC to a nonstop UA-operated flight if P is available? I imagine it's against the rules on paper, but is their system smart enough?
(Bonus question: How the heck does an I -> P change work with a partner? Is this doable only because of the JV?)