I don't have any idea about the UA fuel policy. However, I can say that at the airline I work for, it is perfectly legal and quite common to depart for you destination WITHOUT having the required legal inflight fuel requirements to make your destination. However, you DO have the legal requirements to go to a SUITABLE airport enroute. As the flight progresses, more and more options become available until hey presto, you have the inflight requirements to make destination (Flight Fuel, VR, FR etc etc). If however, the headwinds are stronger than forecast and if you departed with absolute minimum fuel and max payload, then yes, it is possible to not make destination. Result, make a TECH STOP. This is obviously what United did.
i.e. WHO CARES!!!!!!!