# What does xgb's scale_pos_weight parameter do for regression?

From other posts (see Unbalanced multiclass data with XGBoost) and the documentation, scale_pos_weight in XGBoost appears to balance positive and negative cases, which seems to apply only to classification. However, it also appears to be an option in XGBRegressor (see documentation). Before I dive into the source code, can someone explain what this does for regression?

There have been some consistency issues for a while now (I faintly recall nthreads versus n_job issue.)