I found this. Super old but best I could find. Maybe what OP got was only an explanation that they gonna check his request for a refund and not an actual 'refund approved, expect your money in x days'.
https://www.dhs.gov/uscis-refunds-how-process-working-you-questions-cis-ombudsmans-teleconference-january-31-2008
OP you can see, we're all baffled 😁