In colloquial English, it is not uncommon to hear such sentences as these:
It says here in the instructions that you should do this first.
It says on Amazon that the package will be here in two days' time.
To me, these sentences do not appear grammatical: surely it should be "it is said" in both of these sentences, since "it" is not actually speaking, but rather contains speech written by someone else (in the first sentence, by the manufacturer; in the second, by the programmer).
Are these constructions grammatical? If not, then why are they so common in spoken English, at least insofar as they are heard more than the passive alternative?