Did it come up with that route or you used multi-destination?
I used multi destination when searching last night, because if i searched JFK to SFO, it didnt give this option. This morning, when i did i search again for JFK-SFO, it did bring this option up with 25K and a multi-cabin designation, even though multi-destination still showed it at 35K pp.
The really odd part is that i preferred to book it with Lufthansa miles (for obvious reasons), and last night their system was pricing it at 29K miles (so charging for the 2 segments separately), but this morning, once the routing showed up directly on UA.com, they priced it for 17K as it should (even though i had to feed them the individual segments as they couldn't pull the seat doing a JFK-SFO search, i guess because it was 2 cabins).