Yes... but that doesn't preclude there being separate master tapes in NTSC and PAL. The side break issue is obvious -- even different PAL LDs from the same master have different side breaks. But different framing in the middle of sides? Different film flaws? Different video flaws? Different frame counts at reel changes? That does not sound consistent with starting from the same master to me.

I'm not saying you're wrong, but I don't think you can know to the degree you assume. My empirical evidence suggests PAL and NTSC LDs do not come from the same masters.