ExtraTreesRegressor criterion As I understand, ExtraTreesRegressor from sklearn works by doing random splits instead of minimizing a metric like gini for classification or mae for regression.
I don't understand why there's a criterion parameter, as the criterion for the splits should be random.
Is it just for code compatibility, or am I missing something?
No, extremely-random trees does still optimize splits.  It does only pick one random splitting point for each feature (out of those randomly chosen max_features) but then which feature is actually used for the split depends on the criterion chosen.
https://scikit-learn.org/stable/modules/ensemble.html#extremely-randomized-trees