We were on this cruise as well. So many here jumped to the conclusion that the OP had no doubt misunderstood what the captain really said, well he said it, and it was broadcast to every room on the ship, he took full responsibility and did not "lie" about why and what happened, in fact I found his forthright explanation a breath of fresh error. The op's question was "is this fair"?
Everyone's fair is different, for me it felt fair. the best whale sighting I have seen on Alaska cruises were in the inside passage, they were close and plentiful, but I have seen them, they haven't and likely never will. If he never said many people would not even know what they missed.
Another fact is about half the passengers did a 14 day circumnavigation around Japan and the trans pacific 16 day follow on. The 16 day transpacific was 1/2 the price of the first 14 days. A OV room was under $1000 for the 16 days so think $100 off your next cruise, nothing i would jump at.
For the room we booked for 30 days we should get around $800. Enough to do something, although at this point i haven't seen anything posted to my account. It also said you must book it and use it within a year.
My point is not everyone will get any significant benefit from this offer.
Finally, when someone has 40 posts, it took a lot for them to post something, those of you with many thousands of posts are often quick to pounce, back off a bit please!