Why Voynichese doesn't have cribs?

[oshfdk]

If it is a one to many cipher, where a plaintext word can have many possible encodings, there still can be Zodiac signs and planet names all over the astrological section, but they would be different most of the time.
On the other hand, if we treat the manuscript as a faithful rendering of an unknown language in an invented script, this lack of cribs seems to require some explanation.