This very property is
exploited (in a way) by Sukhotin's algorithm to
separate vowels and consonants. Interestingly,
the space character has a variation in preceding
and following characters which is marginally
higher still than that of vowels.
That last property is also observed in the Voynich
MS. I made the calculation many years ago.
I made a 'scatter plot' (every point representing
a character of the alphabet) plotting conditional
entropy of the preceding character vs. that of
the following character. The character that
appeared furthest to the upper right was the space
character, both in Latin and in Voynichese.
So, I don't see anything particularly suspicious in
the VMs spaces.