Forum:XBox Operation: Anchorage Achievements added without installing

Hi.

I bought Fallout 3 for the XBox on january with no add-ons (and it was a mistake: now I know I should have bought the Game of the year edition... but it was too expensive!) and I see all the F3 achievements... and the ones for Operation: Anchorage, though it is not installed.

Is this normal, a bug or what? I do not see the point in getting achievements for one add-on that I don't have, as I don't understand why I have the O.A achievements but not the ones for the rest of the add-ons.

Just curiosity... I love to see all the achievements checked out!

It seems I'll have to buy O:A, still, it seems strange...