Being in *A has nothing to do w/ the possibility of NH accepting your request.
UA has your money in the bank, not NH. Since NH is taking you, they want your kizzash, so they could have refunded your Y fare on UA and then booked you on their flight (I think there's a "behind the scenes" way that airlines can do this without you seeing a refund on your CC, then a charge from NH).
If you were on a W, T, or S fare, you can rest assured NH would eschew you away like the pond scum you are.
