Also, if you click on Advanced on the left when looking at the gallery, you'll see something that is ticked saying "Include Unowned Content." My assumption is if you untick it, you won't see creations that contain anything you don't own.
I also just tried to get a sim with a CC shirt on. When she appeared in my create a sim window, she had only her bra on.
However, I could still see her with the Include Unowned Content not ticked. But I think the people that are doing this type CC are replacing one of the existing presets on an EA piece of clothing. So while I own the tank top that she was wearing, I didn't have that preset.