I don't doubt your story.
But, I just took a few minutes to peruse the NCL site. Looked at anything to do with dining, add on package (to FAS dining), FAQ's and T&C's.
Not a word about transferability. Or multi-use meal vouchers.
Now, I can understand if the meals cannot be, literally, given away (it's in your name and you can't send your pal in their trying to claim on your voucher.
In my suggestion, it's your voucher, at your table, and you are entitled to use it when you want.
And NCL loses nothing, theoretically - they only give up the expected number of meals. Anyone else was not compelled to buy in.