I struck out on that search as well. I even went looking through some old journals on Jstor, hoping an article might make some passing comment about schizandra's flowers with no luck. But it sounds like your observations have you onto something, so thank you for sharing! And fingers crossed your efforts yield some results.
I guess I should add that I came across the term "heterodichogamy", which, from my attempt at understanding it, appears to mean that, within a population of heterodichogamous plants, there are two morphs: some are protogynous, while others are simultaneously protandrous, allowing them to cross-pollinate with each other during both phases of the sexual progression of their flowers. Being that the article was well beyond my mostly forgotten highschool biology education, some confirmation that I'm understanding that term correctly would be appreciated!
But if that's the case, I hope that article we both saw mentioning schizandra being dichogamous would have indicated if it were actually heterodichogamous, or else the plant's protogynous/protandrous identity might depend on the "morph" one has.