This is not accurate.
The requirement is not 3 years as permanent resident, but rather includes any other forms as temporary resident such as TFW or Work Permit etc -
In order to apply for Nexus you have to have PR but the time spent in Canada as TFW / Work Permit counts -
Including myself many many others have received Nexus Basis recent PR award but majority of time spent in Canada basis Work Permit.
Let me get this straight, I've lived in the US for 3.5 years on F1 Visa. Recently I received my canadian PR. Does that make me eligible for NEXUS?