Wonder if the red chempadek is really orangeish, like in that photo? Like the famous Borneo red jack that is really orange? Or it could be like that red fleshed avocado, and be a mistaken identity? A good candidate look alike would be Artocarpus anisophyllus...that really does have red flesh. The exterior of the anisophyllus looks more like a marang, with the little short soft spikes. Ofcourse with Photoshop you can make anything look red.
About chempadek cultivars, a book from mid 1980's from Brunei lists over 50 chempadek cultivars. I think in USA we maybe have 2 maybe 3, and extremely difficult to get even those 2 or 3 cultivars.
I think Frankies is the only one that carries them.