I would suspect they were pan-and-scan rather than open matte. Open matte means the film was shot at 4:3 ratio and the top and bottom were cropped in the theater to give the wider 1.66:1 or 1.85:1 ratio. When the video is presented in open matte, you get more picture information at the top and bottom of the frame than what was shown in the theater.

Pan-and-scan means that the film was shot in the wider aspect ratio (usually 2.35:1 or hard-matted 1.85:1) and then the sides are cropped off to make it fit a 4:3 display. Information is lost from the sides of the original and often the area that's shown is panned or scanned to make sure that the section of the film with the most visual elements or action is visible.