Apologies for being so dense about this... I understand now how when one "changes" a round trip ticket that both legs get repriced (or something like that.) So when I changed one flight on a round trip it repriced both legs and the leftover miles were re-deposited into my account, nice!

But now I have a different one-way that has dropped 20K points (from 40K to 20K, oof) and as I can't play with a different leg to have it reprice the entire ticket, the only thing I can do to keep the exact same flight is to cancel and then re-purchase. Before I pull the trigger, does anyone know if the miles will just redeposit a la WN, or if there's some kind of caveat, like having to use the refunded points within a certain timeframe?

This is what it says online, so I'm reading this to mean I can just cancel and re-book it for 20K point savings. I hope that's right!

"If I cancel my award ticket, will I get my miles back?

Yes. Once you have canceled your ticket, and paid the cancellation fee, and requested that the miles be redeposited, your miles will go back into your account, and any taxes paid will be refunded. The call center booking fee, and the partner award fee are nonrefundable."