Why is there even a Voynich B?

[quimqu]

This is bizarre.  The words "nao" ("não")  and "os" (for instance) should be strictly Portuguese in 1899 or 1999 spellings (DC1 and DC2), "nau" ("nãu") and "ci" strictly from the phonetic spelling (DC3), and "los" and "pero" strictly from Spanish (DC4).  But they appear across those three topics.  Although topic 2 seems to be mostly Spanish, while topics 0 and 1 are mostly a mix of official and phonetic Portuguese words.

The reason some words appear in the wrong topic is that NMF doesn’t know which section each word comes from. It only looks at word frequencies and how words tend to occur together across the whole dataset. Because of that, topics are not exclusive. The model can assign a word to more than one topic if it helps to minimize the overall reconstruction error.
Frequent or function words, like “os”, “la”, or “que”, behave very similarly across all texts, so NMF spreads them over several topics. Also, because the model uses only three components for four writing systems, some words that are similar in spelling or usage (like “nao” and “nau”) end up mixed between Portuguese and phonetic topics.
NMF doesn’t make linguistic judgments. It just finds statistical patterns, and some overlap between topics is normal (it is language agnositc).