Thats pretty much irrelevant. GPU ram isn't used that way at all. Its used to hold the 3D geometry, bitmaps, bump maps etc of assets and other processing data which is largely if not completely independent of screen resolution/no.of screens.
For real-time rendering of a simulated environment - that is, gaming - textures are generally stored as mipmaps so the more pixels it's going to take up on the screen, the more detailed version of the texture is used and thus the memory use rises accordingly through the entire pipeline. It's pretty easy to see if you keep resolution or texture quality constant and vary the other. If you're doing some other kind of simulation that might not hold, but for gaming what you said is pretty much false.