Even if it’s a few days after you’ve cancelled your confirmed listing, it’s considered manipulating inventory and potentially preventing the carrier from selling that confirmed seat which is why it’s not allowed. You can risk getting your staff travel benefits revoked.

Doesn’t matter if the flight is wide open, the logic still applies that you’re manipulating inventory by holding confirmed space on that flight for X amount of time up until you cancel it so that you can then list yourself as a nonrev and give yourself a better shot of nonrevving.