By way of an update, the refund processed ASAP and was reflected on our credit card within 2 days.

I requested that Delta refund my $300 in award redeposit fees. While I received a nonsensical response to my email and wrote it off as nothing (the response was about checking my refund status and a 7-10 day turnaround), I have a credit on my amex for another $300 from Delta.

I assumed I'd be using my amex plat airline credit to eat $200 of the fee but the $300 refund is definitely from Delta and is much appreciated.