The Minecraft client doesn't lie, unless you've modified it. If you're not whitelisted, tells you that you're not whitelisted.
You posted that the sessions servers were unavailable. That means the sessions servers were unavailable. If you can cannot to other servers, that means they have premium account authentication off, which means you may login without checking with the Minecraft session servers. That also means you can choose whatever username you wish, and can hack other people by using their username.