Good spot, thanks for sharing! We've submitted a ticket asking for it to be fixed.
A bit about it, if anybody is interested.
A long while back we launched play.runescape.com which is a bit of a 'are you looking for RS or OSRS?' page, and it's the default experience for anybody landing on runescape.com for the very first time (basically cookie-less visitors), usually it's people who played a long time ago searching for, say, 'RuneScape' but wanting to find OSRS. From there they can navigate to the Old School version (FWIW: A/B testing has confrmed it is a much superior flow versus how it used to be).
The problem here is that both RS and OSRS versions of the pages are sharing the same Membership website component, meaning its inaccurate for us. We'll get that changed.