Yes, I believe that was indeed the case.
Check the last slide on this post for the Mac package.
http://forum.square-enix.com/ffxiv/t...=1#post2836363
You have to buy the game for each platform you want to run it on, but the account and subscription is only a single monthly payment. So, you'll need to pay for any additional client you want to use, but it's a one time charge.