You have it correct.

Screen of Green is where you flower only tips of the plant. By the time you poke all the end tips through the screen the light will not penetrate worth a dam. You can add sidelight but then it's not a Screen of Green.

SCOG is top light only so you only get the tips of the branches or main colas that are long enough to poke through. Once they do and fill out (you still need fan leaves) there is no light for the rest of the plant. If you lollypop it then the plant will not put energy into saving the lower parts of the plant and trying to flower them. You want the plant to put all it's energy into flowering the tops.

Hope that help.