Yep, definitely scratching my head!!
They were just looking at it from an investment standpoint and putting all the apples in one barrel. They are looking at the cruise line corporation, not the cruise line itself, which is why they're not showing such cruise lines as Holland America or Princess, since they're under Carnival, or Celebrity, since they're under Royal Caribbean, etc.
But traveler reviews are skewed anyway. For example, those who travel Carnival on a regular basis know what they're going to get and when they get it, they're happy. But if someone who travels on Celebrity on a regular basis were to go on Carnival, they're more likely to say how bad it is. So, when you simply look at the overwhelming number of past guests of Carnival traveling on Carnival versus those who are aren't happy with the Carnival experience, the percentages are always going to be lopsided. In other words, by the very nature of the reviews being utilized, the statistics are always going to be convoluted and distorted.
Not trying to pick on Carnival and I may not have stated that very well, but I learned about such things in my theories of probability class in college.
To me, if I were looking to invest in any company, I would consider some of this information, but it would not play an important part in my decision. Past history, growth potential, future investments being made, and many other factors would influence me more than stories like this one.
So you just have to take it for what it's worth; not much.