I generally agree, though I understand that people want a reason why the Christian imagery was obscured. This will have to be found in the reason why the makers obscured the
entire manuscript, including the text. The fact that the text is obscured does make it more acceptable that the images are
also obscured, but it doesn't tell us why.
Regarding the tripartite world, I learned only recently that the host was also often tripartite. In this case, it didn't matter much which part was up, since the connection to the world had become secondary.
See Cary's post You are not allowed to view links.
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Login to view., and especially the final image, where the tripartite bread in the middle of the table is like the earth in the middle of the cosmos - yet the T is upside down.