I was under the impression that you could use background's from any approved source. I'm now being told that I can't use Haunted One because it's not from PHB or ERTLW. Can I get some clarification?

In my defense: I saw this on page 5 of an FAQ "What’s Up with the Haunted One Background? The Haunted One background is exclusive to the Curse of Strahd story origin, but is now open to all characters. Errata regarding this background appeared shortly after release. The errata is summarized as follows."

I saw this in the Oracle of War document: "Players can create their own backgrounds, as explained in the fifth edition player's handbook, or use one from approved sources"

and then I've read from multiple places that there are no background restrictions in AL.

The only thing I can find that could possibly negate all of what I just typed is in the Oracle of War document it says "Background. Choose or create a background using the Player’s Handbook or the Eberron: Rising from the Last War campaign sourcebook. You may also choose backgrounds from this document (see “Backgrounds and Patrons”). These backgrounds are specifically tailored to fit into the storyline of the Oracle of War campaign."

sorry if formatting sucks I'm on mobile