Voynichese Phonotactics

[Emma May Smith]

The two examples you give above, oy and ey, can be paralleled in the behaviour of other vowels and don't need to be explained as y acting like a consonant. Thus:

oy (146 tokens) is parallel to oa (282 tokens) and oo (84 tokens)
ey (4025 tokens) is parallel to ea (448 tokens) and eo (3454 tokens)

But if you consider word-final occurrences only, the stats will look different.  oa, ea, and oo are going to be nearly non-existent.

Word finally is a specific position. The character a mostly doesn't occur word finally because it seems to be conditioned by the following character. So oa and ea are never going to be common, indeed, they're just variants of oy and ey anyway.

oo is not particularly common, but many of its occurrences are near the beginning of a word in the string qoo. The five occurrences it does have word finally may be statistically appropriate (I don't know).