The research is pretty poor. The main problem is that all physical punishment is landed into a single pot, but there is clearly a world of difference slapping a fifteen year old in the face and slapping the bottom of a four year old.
If the general practice can be effective depending on fine distinctions, and if such fine distinctions exist, then they matter. General advice like given above is then just bad advice.
See here for a useful meta-analysis: https://link.springer.com/article/10.1007/s10567-005-2340-z