Feel free to correct me if I'm wrong, but, this information seems rather damning for the orthodoxy...
Deaths were registered, tracked and traced, in triplicate unless I'm missing something, and put into the death books.
I think they will focus on the quantity of Jewish deaths actually confirmed in this way (i.e. with official, contemporary reports/documentation), which is of course relatively low compared to the total number of Jews in question. Nonetheless, this process is documented whereas the millions of Jews' worth of ash-remains being disposed of in bulk (into a river, farmland, or into the wind) is not.