Well, he was a Nazi and he was discredited by his peers...
This is a commentary by someone who did extensive research on Reche and his work:
(I must) point out the scientific fallacies upon which your claims and evidence are based. Otto Reche is a good example of this - here we have a nazi by choice and inclination, whose work was so bad that persons such as Robert Procter, Hermann Graml, Edith Zerbin- Rudin, Stephen Gould and Robert Leakey have discredited it. I explained why in more than one post, as I explained why anthromorphic photo comparison is a subjective science with a narrow degree of scientific certainty, no matter how many graphs, charts and measurements he might have had. It doesn't matter how many graphs and measurements he had, if the foundation has been taken away, does it? Advances in the science of mtdna recovery alone, has proven that his foundational base, his sampling of "long headed Europeans" is false. among other factors such as age, the His photographic "proof" is also false - photo comparison cannot account for the thickness of muscle, fat, skin or bone,among other factors such as age,mechanics of photography and printing and other variables involved in photographic comparison.
There were several of these Nazi anthropologists who were revered at the time, but now criticized. On the history channel they tell of a team of them who traveled to Tibet in the 1930's and 'proved' by facial life masks that the Tibetians were really descendants of aryan Germans from the Rhine Valley. This was one of Hitler's pet theories, however, it is now known to be false. So these Nazis were not as respectable, reliable and accurate as Anderson supporters will have you believe. Therefore, doubt is cast on their 'identification' of Anna Anderson being an 'identical twin' of Anastasia.