I applied for Global Entry in 2017ish, and at the time it didn't use login.gov. I renewed my passport and had to update my passport number in the system this year, and that was my first exposure to login.gov. So sometime between 2017 and 2021, they started using login.gov.

The process for establishing identity for login.gov was frighteningly easy. It required something like my Global Entry ID and my full name only, and then it automatically connected with other details about me.