The qualification “ʿinda al-mutakallim fī al-ẓāhir” means that attribution is assessed in relation to what the speaker outwardly treats as the real agent.
Believer’s statement: أَنْبَتَ اللهُ الْبَقْلَ — God caused vegetation to grow.
Speaker who treats spring as the agent: أَنْبَتَ الرَّبِيعُ الْبَقْلَ — Spring brought forth vegetation.
In the second case, if the speaker genuinely regards spring as the actual agent, the utterance can be literal relative to that apparent belief, even if the belief is erroneous. Similarly, a knowingly false “جَاءَ زَيْدٌ” remains an attribution of coming to Zayd; falsehood alone does not make it rational metaphor.