Yes, I am 100% certain of what I said. These individuals have had valid visas in the US and been here for 10-20 years and intentionally have never become green card holders.

One was on a student visa for undergrad and then a student visa for masters for 6 years total (4 for undergrad and 2 for masters), then on a G4 diplomatic visa while working at the World Bank for 5 years, then back to a student visa for 5 years pursuing a PhD, then back to a G4 Diplomatic visa for 6 years while working at the World Bank. This person married an American about 10 years ago and still never pursued a green card out of choice.

Another was on a G4 diplomatic visa while working at the IDB for 3 years, then a student visa for 5 years while pursuing a PhD, then a visa while working at the Federal Reserve for a number of years (not sure of which, but either H1B or J1), and then on a G4 diplomatic visa while working at the IMF.

Of course, these are not your typical situations for the average immigrant. Admittedly, I live in a bit of a bubble surrounded by economists in Washington DC from the World Bank, IMF, IDB, etc who are mostly on G4 diplomatic visas.

My point is it is still possible and one shouldn't presume.