He's not, but that doesn't matter. You're going to be hard pressed to only ever communicate with professional communicators with good attitudes your whole career. So if you ever want to be taken seriously and have a successful career, you're going to need to learn what battles are worth fighting. Hell, maybe it was even a test to see if the guy worked well on a high-stress team. If he can't handle one person not understanding the difference between Unix and Unix-like, how's he going to handle someone who puts a tab as an indent instead of two spaces?
The recruiter was wrong. But it doesn't matter. Stanley (hopefully) learned a valuable lesson here, and that lesson is "pick your battles". Life, especially corporate life, is full of nonsensical requirements and TPS reports and if you fight every single one of them your performance review will read "not a team player" every single year.