Voucher Unpost - Reversal Entry - BU default - used closed period date

PSOFT 9.2 - Payables

I have a voucher from 2022 that we did a unpost/repost on. The reversal ended up with an accounting date from 2022 (original accounting date on voucher). I figured out this is because the user did not change the Reversal date from "use BU default" to current date.

So now I'm trying to figure out what I have setup wrong on the BU that allowed the system to use an accounting date from a closed period. Can you tell me what this "use BU default" setting on the Voucher Unpost page is looking at on the BU setup pages?