I think you nailed it Michael. D. tsaratanenensis is what D. 'white' was sold as, but it can't be. It doesn't even come close to the description in Palms of Madagascar. And at the time of POM's publication, the true D. tsar. hadn't been been seen for 70 years. I have some pics around here somewhere of Bo's. His are about the same size as the one you posted.
So for now it's just another 'Mystery Dypsis,' not to be confused with another previous 'Mystery' known as D. 'white petiole.' That mystery was solved with Don Hodel describing this previously undesribed species as Dypsis albofarinosa.