In theory, the LB should be at an ECC boundary - that's where the multiple of 16 comes in. However, who knows how studios master their DVDs these days! I have seen some shockers recently that are obviously out of spec but released on an unsuspecting public.
If you have a direct ISO copy of what's on the source, then there's nothing you can do (if you want a direct ISO to burn methodology) - except be happy that ImgBurn has adjusted the L0 zone for you. In the future, I'd start off by having files, not an ISO.
Regards