I specifically called and asked if I could UG ORD-BOS. Was told no a few times. Eventually an agent said yes, split the flight into 2 separate segments and put me on the UG list. Then, about a week before I left, I was booted from all my seat assignments. I called back and a supervisor told me they never should have split the segments and my reservation was "illegal" or otherwise not valid as-is. They had to move it back to a single segment, and in the process get yield management involved to override some stuff because my initially booked inventory was no longer available.

I was told I could ask at the gate at ORD for an UG, but by then all of F was long gone.