Let me ask it this way: what makes you think that this report is credible, factual and trustworthy?
I already answered above. It fits into the picture of historical accounts of Stalin and of how bias and interests work in regards to a nation state and it's geopolitical competitors.
You're convently ignoring the context in which this document exists and how its content relates to it.
It’s almost like finding a book in a library and believing it to be credible because it’s a well known library that has that book
Your try at abstracting something this complex fails. It's more akin having two libraries with two different accounts of history where some books are deliberately hidden (for various reasons, it exists and wasn't destroyed). This is a now a made-public book confirming the other libraries accunt history with their own source
Also:
The CIAs work is sloppy and they lie to themselves in their top secret documents. It was a soviet double agent collecting this