That is correct. Some pressing plants were more prone to creating such discs. IIRC, it involved the glue used to adhere the two sides to each other.
"Something I've recently discovered and will be doing for my DVD's is a process called TOOT, which basically compares three different sources of video to eliminate any rot spots or other noise."
I will be doing this frame-by-frame for my anamorphic version. If one frame has a "glitch" somewhere in the scene, I will copy/paste an identical glitch-free section from the previous/next frame. Vegas makes this exceptionally easy.