OK, so my bright idea was to go into OneNote (Desktop) and “Save As…” to another location outside of the:
%homepath%\Documents\OneNote Notebooks
…directory. Bear in mind, moving this will not accomplish the same thing as OneNote (Desktop) will track where you moved it and of course you also cannot save anywhere within that directory or OneNote (Desktop) will find them and promptly remove them once deleted from the device.
I put my newly synchronized mobile OneNotes into:
%homepath%\Documents\OneNote Notebooks - NoSync
…I know, super-genius creativity is hard to even grasp with a normal human mind — I forgive you.
NOTE:
Re-verify all of the above actions as I found what I believe to be an unrelated option that shouldn’t have affected anything but who knows… ?