Scott Alexander wasn't worried about readers of Slate Star Codex finding out his real name, he was worried about patients who knew his real name finding Slate Star Codex. Using a pseudonym on the blog was a reasonably effective trapdoor function.
Publishing under your real first names, and letting people know where you work, is pretty far from "perfect isolation", isn't it?
He's not stupid. Why did he chose such a terrible pseudonym?
Retconning SSC as an "anonymous" publication is silly, though, and really dilutes the efforts of people who truly want to or need to remain anonymous.