No; change fee means change fee, and it is always payable (except when there's a waiver, like you have been posting about already today)

Fare difference is only chargeable if there is actually is a difference in fare. (This is to stop people like you buying a seat on the cheapest flight of the day, then rocking up to seat yourself on the most expensive flight of the day. But in some cases, the new flight will be cheaper than the ticket already held, so there is no "fare difference" (they never refund the balance if you go cheaper) and therefore only the change fee is payable).