I think you're both right.Wrong. The exchange didn’t open for the Southampton game, so I didn’t list mine. I got the naughty email.
Warning emails have been sent this year for non-use/non-listing.
Next season there is a definitive 2pm day before cut-off for listing to not make the naughty list. You will still be able to list after that and, if the ticket sells I assume you won't get a black mark against your name.
If you list same-day and the ticket doesn't sell (or the exchange doesn't actually open) then that's when you will enter slap-on-the-wrist territory.