I think it probably is because of Coronavirus, and I suspect offer might be extended beyond 16 March.
From what I can make out the new flight would need to be the same as the original flight, ie if I book a standard economy flight I would only be able to change it for another standard economy flight to the same destination. Of course flights at certain periods (high season) are going to be at a higher cost, so I don't know how that works.
They are not offering free cancellation, just change of dates.
This is the promotion