Usually if they don't specify a version, it's the original release. I know this isn't 1.5, because I don't see an arachnophobia mode in the settings list. Luckily 1.5 is mostly just bug fixes and some seemingly minor QoL updates, so if you know how not to break a save you shouldn't be missing all that much. Still, I'm enjoying it a lot, so I'm putting in an update request regardless.