I'm actually torn on the idea that he didn't finish a game and reviewed it. On the one hand, yes, to be able to review something you must have a good understanding of it, at least for it to be a professional level review, rather than just an opinion. However, with games a reviewer shouldn't always be expected to have done all the content in a game for the review. Let's look at Dragon Age, Skyrim, hell, the Souls games. All of these are games which have a bountiful amount of content to explore, to expect a reviewer to play through all of this is simply absurd. With a book or a movie or an album, all the content is easy, straight forward, linear, you can have it done in a matter of a few hours or days. Some video games can have weeks worth of content. Hell, there was a side quest in Final Fantasy 9 that wasn't discovered until at least over a decade after the game came out.
While I get that the main storyline is generally the accepted part of a what constitutes whether a game is beaten or not, it still seems a bit weird that that's what we draw the line at as to what has to be completed before someone can be deemed worthy to review a game. Talk to anyone that has played a Bethesda game and they can tell you how lost they can get in the side content, and honestly how the main storyline can even be boring and uneventful by comparison of what else the game has to offer.
As for a game that is heavily story based, that becomes a little bit more of a necessity to complete the main storyline, however, in a game like Final Fantasy 13 where the gameplay doesn't suddenly change near the end or anything, I believe I can say if someone just watched the ending on youtube they'd get a close enough experience with the storyline, and they already have done the gameplay, that ultimately they'd still have a good understanding of the game.
Those are my thoughts on that situation at any rate.