I think much of what you say is correct, but the legal stuff just isn't correct. When a contract for travel is sold to someone in Country X, Country X has jurisdiction to address what it determines are its rights. If a company does not want to comply with those laws then it better not sell its travel product in that country or through agents in that country.
I find many EU laws to be overly gratuitous and quite costly to companies...far moreso than the US. But they are what they are.
So rough seas are contemplated. What occurred most certainly was not. You may disagree, but that is pretty much what the law is.
Now is a good place for me to repeat the question I asked far more whent I sold more mass market cruises, "If your experience was so bad on that cruise line, why would you want a free cruise on it? Wouldn't you rather spend your time on a cruise you liked???"