The attribute of speech must be distinguished from its expression. The first concerns the speech that subsists in God; the second concerns human recitation, hearing, inscription and the different arrangements of revealed texts.
Counting the words of a surah or naming different scriptures is an intelligible linguistic exercise. It is not a count of parts within an eternal divine attribute.
This distinction makes it possible to affirm at once that all revealed books are divine speech, that the divine attribute is one, and that the recited forms differ.