Let there be meaning

[ReneZ]

As long as cipher text word boundaries differ from plaintext word boundaries, I guess, these frequent chunks of cipher text could correspond to common subword sequences in the plaintext. E.g., the following are the 20 top frequent 4-letter sequences and their counts from Opus Majus, about 4% of the whole text are these patterns.

Fully agreed. However, a one-to-many cipher would also break up such correspondences.