I only recently learnt about why Transformers Zone has only ever been released as a dodgy fan-subbed video on DVD instead of a proper high quality master with non burnt-in subtitles, as is standard. And also why Zone is a Special Feature, not a main feature on the last DVD of Victory.
It's because Toei refuses to license OVAs outside of Japan, and including Zone as a low-quality fan sub as a Special Feature is a legal workaround. Apparently this is also why Scramble City has never been released on DVD outside of Japan.