I don't know how rigorous the OP's analysis was, as it could come down to reduced availability on a particular day closing out lower fare buckets.
The market anomalies can work to your advantage though. There are often some very nice Gulf-USA business fares (AA fare codeshare on BA flights) that work out cheaper than a straight return to LON !
e.g. currently available:
BA I class DXB-LHR rtn in April - AED 12410
AA I class DXB-JFK rtn in April - AED 12230
Free weekend in NYC anyone ?
Fares ex-Gulf often have more flexibility or much lower change/canx penalties. e.g. USD160 on the above AA fare.