Not so much a hoax as a whimsical prank.
Worthia remusng dorplat igmungium. Dowtop soldera ya de manga
What I had read in a different article recently was that many of the plants depicted in the book were recognized as Mexican, and the language was found to be an obscure Aztec dialect. The speculation was that the manuscript was likely written by a native convert soon after the Conquest.
Not so much. During the time period that this was written in, seeking secret knowledge was often frowned upon and even persecuted. Those who still sought to seek the unknown would create secret codes that weren’t easily broken.
So while this particular book may not have been that important in the realm of the sciences, it may have been done to protect what the author discovered that was previously unknown.
If so, then it is a very lengthy and elaborate prank.
I suggest that it may have been the work of autistic person. In the past they were called 'eccentric' but it seems their mental abilities were a step above most of humanity. I could easily envision someone like that creating this book, and their own language. A book written by someone who never planned to have anyone else read it. It may have been a personal diary, depicting his(her) view of life.