I used this code a few times a year or so back.

For one of the tickets I canceled it within 24 hours, but then got an email saying that due to it being a discounted ticket there was no refund due. Despite pointing out the legal requirement for them to refund, they refused. Eventually I had to go the credit card charge-back route and it was resolved almost immediately.

After that experience I gave up on using it as not worth the extra few percent savings. No idea if this was just a one-off and/or a bad agent, or if there are actually additional special conditions around these discounted fares.