Thanks! I hadn't seen the FTB guidance for example 5. I think the tricky bit comes when you plan to live in another country for an indefinite period of at least several years, but not forever (and without any specific return state in mind), and keep a storage unit (in California) with some stuff that you want to keep, but don't want to move to another country because of the expense.

FTB can use 'has a storage unit in California' as a factor; and maybe combined with California banks and California voting, and maybe a California mailing address, if you use friends/family to forward your mail, could be enough to tip the scales for them. It's rather opaque.