I'm pretty sure it's all because a flaw in the EA Desktop app. And support doesn't know what they are talking about because there's no communication between them and EA Desktop devs. -_-
When a game asks Origin/EA Desktop which DLCs you own it usually sends a "group". And Origin/EA Desktop is supposed to return just the DLCs in that group. And EA Desktop just dumps everything you own. -_-
I have confirmed this is an issue with Need For Speed: Most wanted and probably the same happens with The Sims 3. And this thread sounds like the same stuff too.
