I think hot breakfast options are only offered on transatlantic flights out of LAX/SFO. UA 922 IAD-LHR is a day flight, where I guess you get two main meals in C
That's it exactly. We had a thread on this recently, which I can't find just now.
West Coast to Europe evening flights - hot breakfast option.
Chicago and East Coast to Europe evening flights - continental breakfast only
UA 922 - hot breakfast option ('cos it's the first meal that's served)