Believe it or not, I watched the old Alt-Right form online (never was a 4chan poster, though). Saw it form from roots in Neo-Reactionary and libertarian (specifically, a weird authoritarian libertarianism back when Pinochet posting was still trendy). So even though I don't keep up with the extreme Right-wing anymore (aside from the taste of it on Kiwi Farms), I have a good sense for it.
Something about the snippets of manifesto I've read just don't read right. It's like you said, he doesn't talk like a Rightist, he talks like somebody talking about the Right. I'm not convinced its a glow-op or anything (but glow ops are definitely real, the Spanish government used to do them against Anarchists all the time), but it puts me off in a way that other manifestos (like, say, the Texas Wal-Mart shooter) don't.