What is the ruling on naming Sibawayh's book "The Qur'an of Grammar" and is there any Sharia-related reservation in that?

It appears there is no harm in metaphorically using the terms "Qur'an" or "Mushaf" for something other than the Book of Allah the Almighty, as a figure of speech and a كناية (metonymy) to express the utmost perfection and precision, provided there are indications that remove any ambiguity. Scholars have used this to describe meticulous narrators, such as Mus'ar, by calling him "the Mushaf," and to describe certain books like "Sunan Abi Dawud" and "Kitab Sibawayh," which was called "the Qur'an of Nahw (grammar)" due to the precision of its content. Nevertheless, it is preferable to avoid these appellations and exaggerations, and to preserve the revered status of the Book of Allah, especially for the general populace, as such usages are permissible for scholars who can distinguish between literal and metaphorical meanings.