Notocactus ottonis vencluianus

Notocactus (Parodia) ottonis 'vencluianus' is considered a flower color variation of common yellow-flowering species. The plant stem does look a lot like that of N.ottonis, but I've not heard of successful crossing of these plants. Than may indicate that this is actually a different species all together, another example of converging evolution in Cactaceae.
The flower color is somewhat too bright and almost hurting to look. It is somewhat unclear to me why this form is not seen more often in collections, as growing it not any different than growing any other Notocactus, and seeds are readily available from many good sources.