There's no "conveniently forgetting" about it, and there's nothing to refund. Rerouting is always done on an even-exchange basis. A savvy customer traveling on a one-way ticket could refund and rebook if the walk-up fare is less than they paid, but this is something different. The more expensive fares allow, but don't require, transportation on a lie-flat; the less expensive fares do not. Someone who finds themselves in that situation should not expect a refund, but rather should consider alternate dates / routings that preserve the lie-flat seat. (Note that I'd expect the inverse to be true too: if you book a cheaper, non-lie flat seat, and you get hit with a schedule change, I don't anticipate any problems being moved onto the lie-flat assuming the routing is sensible). It's not really any different than any other situation where you paid a premium for a given flight (due to schedule, routing, whatever) and then got re-routed.

Is this a change I like? No, absolutely not, although I'd never pay what UA wants for AUS-IAH-HNL in J anyway. But what it isn't is a surcharge for a lie-flat seat, although it acts like one.