As you can see in the screenshot Classic, and Era are both in playerworlds, as well as Zone, but no West.
Zone is on the PC client, as well as a seperate, completely different Era ((PC Era)) and there is currently no hosted Classic server on the PC client to my knowledge.
TL;DR It's false advertising. Zone is, Era really isn't, and Classic definitely isn't.
EDIT: Thats not the playerworld client, thats graalonline.com. You can play Olwest on your computer via facebook.
As relatively new as Olwest (Dec 2014) is compared to the other 3 apps (Classic was 2009, I'm not sure about Era and Zone. But, older than 2014, nonetheless.) And considering how Graal works, which is with little to no consistency to its work, thats why you can't find Olwest on graalonline.com.