Different things can be related to one action: a principal agent, a cause or condition, a time, a place, and an object. Conflating these relations can mislead a rhetorical analysis.
Supplementary illustration: «أَنْبَتَ الْمَطَرُ الزَّرْعَ» — Rain caused the crop to grow. Rain has an intelligible causal association with growth, but deciding whether the ascription is literal or figurative still requires the apparent standpoint of the speaker.
The source uses «أنبت الربيع البقل» because the association between season and growth is easy to grasp, while the rhetorical identity of the attributed agent still needs analysis.