Hi there,
I am in a somewhat similar situation that you are in. I completed my master's in 2018 and have been working as a researcher since and plan to apply for the NSF-GRFP in fall 2020. I actually contacted the NSF and they also said the stuff about the two-year gap between master's and the grant submission date, but they also made it sound like it's geared toward people who are just starting or will start their grad careers and give higher preference to those people. I'm trying to look for people who have had success in winning the grant after completing their master and working for a few years.