Don’t mess with the HDRI image, if it is a correctly captured one i.e. it has all the dynamic range needed to cover the brightest point and the darkest point in the image. This is what will give you photorealistic results. If you want to control the dark side of your object, you can add fill lights or reflectors as photographers would, or do it when grading your render.
He does this in his tutorial because the sun intensity is clipped in his HDRI. He says that you get accurate lighting by doing this trick, but even if it “looks” more realistic, there is nothing accurate about this method.
You can use this method to control the lighting to your liking of course, it’s always good to have artistic control, but it’s not physically correct.