My theory: I doubt Musk had any hands on direct control in the decision. If he did, the feature would probably still be active. My guess is one of the developers quietly pushed the update because, looks around, reasons. It was reversed so quickly I have a feeling Musk was blindsided like most of us.
To more evenly distribute the collected rainfall rather than to just the plants sitting under the edge of each solar row? Or to use the rainfall for other farmy things?