"Write only" means a person understands perfectly well what each individual statement means, but piecing together the big picture of what's going on can take an inordinate amount of time.
Precisely.
Given a passage of text in a language whose grammar is unlike any with which you are familiar (like, say, Chinese) and a dictionary translating the words of that language into one in which you are familiar, it doesn't take that long to reach the point of knowing what each individual word means, while still having no idea of the overall meaning. For me, at least, Chinese fits your definition of "write only" quite well, provided I have a Chinese-English dictionary available.