Nolva Saturation Dose

I’ve been hearing that the saturation dose of Nolvadex is 20 mg/day and that the proper PCT protocol is thus 20/20/20/20.

Either my google-fu is lacking or it’s tricky to find reliable information on this. I’m guessing since 40/40/20/20 PCT is frequently recommended here that most of you disagree that the saturation dose is 20mg. If so, why? How do we know what the proper Nolva dosage is?