Absence of a particular attribute is not the same as absence of every other legal rule.
“Bring a book” does not specify its colour, but it does not permit taking someone else’s book without consent. The properties of the requested object and the lawful method of carrying out the task are distinct questions.
Similarly, recognizing a Qur’anic noun as unrestricted does not isolate the ruling from all other texts. This lesson addresses its initial linguistic indication, not every possible legal condition.