وَيَكُونُ نَفْيًا بِطَرِيقِ الْكِنَايَةِ الَّتِي هِيَ أَبْلَغُ
It becomes negation by the more emphatic method of indirect expression.
A direct denial rejects the specified attribute without an additional step. In this reading, an implication that would follow from the supposed likeness is itself denied, and the denial of the original likeness follows through reasoning.
Calling this reading “more emphatic” is a judgment about this particular rhetorical analysis. It should not be expanded into a rule that indirect speech is always stronger than direct speech in every context.