Have a flight SFO-BOS in January that appears to be a sUA PS 757 (28 J) that says J0, but only 10 seats are assigned and all in the first 4 rows. I know the standard caveat that "seat maps do not equal seats sold" but this just seems fishy to me. Any chance UA is not sure if they will send a sCO 757 (16 J) and so is holding back on selling too many seats?

Curious about how this works, thanks,
Sven