I think I see what you are asking about, the definition of the term Tumble in the context. Your initial quote about the XP-85 model test seems to be an official write-up, and I think that you would have to refer to the definitions used by the writer. I have previously given you an example of a P39 test in an attempt to illustrate the term Tumble being used. I thought that fairly illustrated the term. However, you are still asking. So, here is a further example of an Aeronautical definition. You might notice that this definition makes no mention of being uncontrolled and does not include a specific amount of pitching motion.
Cheers
Eng
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NASA (.gov)
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by WJ Klinar · 1948 —
Notion defined as merely a tumble consists of a pitching motion about the Y-axis. NACA. •. CONFIDENTIAL. Page 18.