blog.Voynichology.net post 4, page 30
What then does the Voynichese-Manichaean script offer
that the other scripts do not?
Several possibilities present themselves.
If it is the case that Voynichese/Manichaean was developed specifically
to write the language of the Arghu/Khaladj branch of Old Turkic,
then it seems likely that geographical distance,
& differing political & social forces may have separated the Kaladj,
whose movements were mainly South & West, towards Afghanistan & Persia,
sufficiently far from the Uygurs in the far East & North around Mongolia.
The Kaladj/Arghu apparently represent
the earliest division of the Turks.
They were even considered to be somewhat outside the larger Turkic tent,
even though they were usually included in the confederation
when they were called upon.
Their language preserves many archaisms
& has a very conservative grammar.
It thus makes good sense
that their language might require a dedicated script.
If the Kaladj were centred around & about Afghanistan,
then it is not so strange that the may have chosen Manichaeans
to develop for them a new script for their language,
as this area at this time was also a great stronghold of Manichaeism.
Nor did the Manichaeans need
any particular encouragement
to develop new scripts.
Writing scriptural wisdom
was one of their deeply held values.