We had a port cancelled last summer by NCL prior to the cruise. We had bought an excursion. I called to get the money I paid credited back. I was first told that we would be getting a nonrefundable credit, and I should be grateful because they did not have to give anything for a cancelled port. I said no I was asking for money back I had already paid, not a credit for a missed port. The representative then told me that she had to consult another department. When she came back, she credited my card back explaining that what in effect was being done was we were cancelling the excursion and were within the time limit allowed for doing that and getting it refunded.
All references to cancelled excursions going to refundable onboard credit actually are true for when this happens on the ship, not pre-cruise.