I don't know if he can read Japanese, I assumed he does when I read the article, since he talks about the main story and all that. Forgot that Nintendo region locks everything, so that would definitely hinder people from buying the a import copy. I also have no idea what the payout is for writing a Kotaku article.
The dude comes off as genuine though based on the article, I don't sense laziness or malicious motive.
He's also their resident anime editor, I think. Definitely speaks Japanese.
He's friends with Kat Bailey from USgamer and recently was a guest on Axe of the Blood God (yes, that's what it's called), their RPG podcast. I can't stand listening to the guy (he was on Active Time Babble a lot, 1UP's RPG podcast), so I skipped the recent episode where he's on to talk about Xenoblade.
I see from looking over it again that this is a "preview" and I don't think it's laziness or anything malicious either-- I just don't get why someone who thinks a game is boring would proceed to pay it for 70+ hours. You would think that spending a few hours, taking some screenshots and video, and then saying "this game is fucking boring" would be enough for this kind of article. Who cares what the fanboys think? You can see from the comments that they're buying it anyway.
Due diligence counts for a lot when people are ready to tear you a new asshole for every little thing. Giving a game enough time is still one of those sacred cows of video game writing, with 'enough' meaning start to end playthroughs most of the time.
Besides, as someone who tried to make D3 a mainstay game and failed, the numbers aren't that weird to me.

I tried my damndest to like it, believe you me. Destiny was the same for many people, from what I hear. A perverse need to understand fully why you don't like it.