I don't know but it's a very good question. I thought I read that there was a resurgence of the idea that phantom and mystic might be a little different after all and lesser X mystic (as well as phantom X mojave) would be good tests.

There have been several recent threads about what leucistic to get to have the best breeding potential and lesser + mystic might be it (presumably a nice white leucistic that could still produce mystic potions bred to a mojave gene ball).