Quite true when using THIS method, but the OP would be well advised to do a dummy booking for a Standard award ticket on his "preferred itin", and scroll over the View Flight Details to determine whether or not .bomb believed there were NC space available. If so, I would suggest a quick call to UA to make sure it's not phantom space prior to purchase of the itin.
Then, QUICKLY, apply for the upgrade. That's the best method for getting your NC space with (relatively) little hassle.

Dave