More data did not mean a better model.
The single-season model (R² 0.851) outperformed the multi-season model (R² 0.772) by roughly 10% because a single regulation era is more homogeneous.
Why it matters. It is a useful counter-example to “add more data”: matching the training window to the decision context beat simply using more history.
Caveat. The single-season model is narrower — it assumes the current regulations hold.