Andrey,
Thanks very much for your comments.
1. Yes, it does seem he made a good-faith effort to get the numbers right.
2. You might well have a point there. He officially toed the Marxist line in his writing, but it appears he might have been somewhat conflicted internally. I found a thesis online that contains a chapter (
https://pure.uva.nl/ws/files/1040555/145206_09.pdf) describing him, his work, his views, and his relationships with his Eastern and Western counterparts. It's a bit long-winded, but it does indicate that he valued the truth, actively engaged with Western historians, and was uncomfortable with, and critical of, some aspects of the GDR narrative.
Regards,
Leon Venter