Agreed.

For a presentation he didn't present very much. I kept listening for him to wrap up his points and drive home a message, but in the end all I got was 16 minutes of how cool it is to be him and a generic platitude about fear and learning. Not very helpful

Unless he started speaking it at the end, he spoke way too little Japanese to be able to judge (I stopped watching after the language part).

He does have more info about language acquisition on his blog, FWIW.

Accent? You can't fake an accent easily. You either have it or you don't, and I'm pretty sure he had it even if he spoke 5 sentences. Who knows about the rest of his knowledge about the languages he claims to know -- he talked about Kanji then proceeded to use words written in katakana as examples.

Good to know about his blog.

I heard only 2 very short sentences (8時に起こしてください and 8時に犯してください）. Even if it's just accent we are considering, you need longer utterances to be able to accurately assess whether it is passable as native. If you listen to a language learner speaking for a significant amount of time in their target language, you will usually notice certain phrases are (hopefully) dead-on native-sounding, but others can of course use improvement.

That's not true: I've spoken single sentences and Japanese people would tell me, "when you spoke just now I thought you were Japanese."

And for what's it's worth, he spoke more than the above (e.g. when he was imitating the instructor).

That doesn't contradict my assertion that generally some things will sound natural and others won't.

When we was imitating the instructor he was speaking English in a Japanese accent right? I am talking about whether his Japanese is native-sounding.

That's the funny thing: he was speaking Japanese but two of the 3 words he used were borrowed from English.

I guess in the end not having been to Japan and knowing few, if any, people who have gone there and seriously studied the language, it simply sounded impressive to me.