It's not complicated. The fare rule is as written, with residual value ignored. United then disavows that rule, to the customer's benefit, for flights that it sold directly. If you purchased through anybody else, the rule applies and residual value is ignored.

There are two ways to look at this. The cynical approach is that UA is trying to drive third parties out of the business and interact with their customers directly. The less-cynical approach is that UA hasn't figure out how to allow travel agents to generate the new form of future flight credit that UA has been issuing, and that the old approach -- generating an electronic travel credit for fare differences -- was too close to a refund.