General intelligence is primarily about developing useful conceptual categories (not mapping to existing ones) and drawing cause-and-effect inferences that assist us in achieving goals.
Curve fitting is just another name for pattern recognition, mapping to previously defined categories. I would personally argue there's no intelligence there whatsoever. Intelligence can't exist without a foundation of pattern recognition, but it isn't the same thing.
Intelligence is fundamentally goal-directed and able to reason, while curve-fitting is fundamentally not.
(There is also unsupervised learning in deep learning, which doesn't use previously defined categories, but since it is similarly non-goal-directed, I would still argue that this is merely dimension reduction as opposed to intelligence -- useful for sure, but not the same.)