فَهُوَ لَيْسَ مِنَ الْمَجَازِ فِي شَيْءٍ
In this respect, it is not figurative at all.
Calling Zayd a “human” is literal: the general word is assigned to the human kind and Zayd is a member of it. No additional class-membership needs to be imagined, nor is the word shifted away from its normal domain.
By contrast, a brave man is not literally a member of the zoological class of lions. Calling him “asad” needs a rhetorical account. The intellectual theory claims that the speaker first imagines or asserts his inclusion among lions and then applies the lion-name on the strength of that assertion.