I usually look up A. hypargyreus to find info on this Red Kwai Muk, not the common name. Botanical names tend to bring me more relevant info than common names, even when misapplied. I consider myself a stickler for correct nomenclature, but that won't do me good if I can't find information, so when posting here, I usually go the practical route: the correct name (if one has already been given), plus the misapplied names for the search engine to pick up, perhaps with a nomenclatural explanation for good measure.
My recommendation: stick cf in there. Artocarpus cf. hypargyreus. That way, folks like me (and apparently several others) will find this post when using the misapplied term, while making it clear that this is not a member of that species. "Confer with", meaning it frequently gets compared to a known distinct species. As an added bonus, we won't have to worry about the fact that it currently lacks a correct botanical name, having only a provisional one that will be removed soon enough.
If the concern is the lack of information available for the genuine hypargyreus (presumably because the red one keeps stealing its thunder), it's still a useful connection to make, as any dialogue involving the nomenclature of the red one will invite discussion on the white kwai muk as well, as you are doing now. It generates the attention, leading to information sharing even for the lesser known species.