Yes, doubt is a healthy thing. It leads us to search for the truth. I'm not sure if you are familiar with Donald Tyson or not, but the editions I have are annotated him. Many of the original manuscripts of such books contain numerous errors (in some cases by the original author, in others by the interpreter) but in either case Agrippa is acknowledeged of the father of many manuscripts that were ripped off by other people- I.E. 'The Magus' by frances Barrett. However, this does not relate to Cagliostro, and I have 20 years of occult study behind me. Tyson is a highly credible and respected Magician ( Ceremonial). Perhaps your doubt will lead you to accurate research and past the "mumbo jumbo" that seems to plague modern times. By the way, if you doubt John Dee's manuscripts perhaps you should drop by the British Museum and take a look at the originals, the table of practice, and the Sigillum Dei Ameth?Theses texts were found in a hidden compartment of a drawer from a desk owned by John Dee. ( Unfortuanetly, the Golden Dawn did not recognize that the manuscripts were meant to be a complete system and seperated the 'Enochian Calls' from the rest of the text. For more on this you can research 'Enochian magc for Beginners' by Donald Tyson. Don't let the title fool you.)
I Find it highly unlikely that someone would go through the effort of research and inventtion of a system of languange equipped with cooresponding symbols and mathematical correspondences (In both books listed) and not list their own name so they could profit from either the reputation or copies of the original. What makes you qualified to place doubt or value in books in my library that you have not seen? Have you reseasrched them? Or, is this, as I suspect, mere speculation based on partial information?