True . . . and additionally, the weight over these land masses have depressed both so that much of it is below sea level, making it a perfect place to collect runoff in the unlikely event that both melt simultaneously.
However, said event is unlikely to happen given that it is summer in Antarctica when it is winter in Greenland and vice versa.
I've run the computations related to those ice sheets melting, including compensation for the "land bowels" which hold the ice. The ocean could indeed rise 10-12 feet. Given the shorelines around the world, water would not penetrate too far inland. There are a few places that would be submerged. Roof tops and telephone poles would still be visible.
If those sheets completely melted, the world would actually remain mostly intact.
But the truth the alarmists won't utter is that those big sheets aren't melting away. They mostly shift around from place to place.