Looking at the N-400 Application for Naturalization Form, I read on https://www.uscis.gov/forms/uscis-early-filing-calculator (mirror):
You may file Form N-400, Application for Naturalization, 90 calendar days before you complete your permanent residence requirement if your eligibility for naturalization is based upon being a permanent resident for at least 5 years.
Demonstrate continuous permanent residence in the United States for at least 5 years. (In some cases, this may be 3 years if you are married to a U.S. citizen.)
Assume a French citizen living in the United States applies for EB2-NIW, then I-485, then gets an EAD card, and eventually gets a green card, with the intent of filing the N-400 form as the next step after a few years living in the US.
When does one become a permanent resident from the N-400 standpoint?