Spoke with Mark tonight at length. Long story short he said he has no problem with referring to these as B/W axanthic. The reason he went with something different is because he didn't want there to be any confusion when talking the two types because axanthic was already being used to describe the blue axanthic (if that's what we are calling them). So as long as we all know what we are talking about from here forward these will be referenced as B/W axanthic. He did want to point out that achromatic does however work as well
His concern is not in a name as much as getting these out to those who want them.