No I don't agree on that. How can you not see that it revolves around Yuna. I feel as though I have to pull examples. Like in Bevell and the Desert, or in Besaid, or all the fuss of Yuna's engagement to Seymour.
Well, the plotline revolves around Yuna, but the main character is Tidus. It is through his eyes that we see everything, essentially. I think this is the distinction between main character and protagonist.
I mean, the same might be said for the Chrono series. Who does CC revolves around? When you get to the end, you see it's Schala. In some ways, the whole series is the tragedy of the house of Zeal. And yet the stories themselves are told through the eyes of Crono and Serge. That's the thing in storytellling. The person who observes things going on does not have to be the one that is most heavily impacted by the ongoings of the plot. Often it is the friend or ally of the observer. After all, sometimes the person to which situations happen cannot feel or understand them as well as someone who sees it happenings. As such, the poignancy can be increased by shifting from the object of the plot to an indirect object. That is the form that FFX takes, as well as something like FFXII (whose battle system I adored by the way, as well as their pronounciation of the names... kudos to them for pronouncing Jagt as it would be in German, rather than with an English J...), and in some ways FFVI. Terra might be both the main point and view of the story for a time, but for most of it you have other characters being the central focus, though she might remain the integral point. FFVII, on the other hand, is through the eyes of Cloud, and about him (well, it might be Sephiroth, but I'm speaking of on the 'hero' side of things.) Knights of the Old Republic falls into this category, too.
All I've got to say about FFXIII is that from what I see is that they finally again seem to have a heroine of Celes' calibre. I hope they make good on it. Ashe wasn't too bad, but missed the mark by a bit.
And yes, I used impacted as a verb earlier there. I don't get it how people say it's not. It is a verb, and always has been, at least in some form for the last two and a half millennia. Just saying that in case some grammar fiend feels inclined to level an assault against me.