True, but many modern computers are using unified memory. On such systems all memory is almost equal, despite often reported differently.
For example, on my 5 years old laptop with integrated AMD GPU, windows 10 calculator in default state uses 33 MB system RAM, 9.6 MB dedicated VRAM. Maximized to FullHD screen, same app uses 36 MB system RAM, 13 MB dedicated VRAM. Maybe the OS counts VRAM as active private working set, maybe the app uses more than 1 buffer.
Regardless of the reason, it’s IMO unrealistic to expect a modern GUI app to consume less memory than required for the frame buffer for its window.
> many modern computers are using unified memory.
Not really true. Even machines with integrated graphics in Windows aren't truly using a fully shared memory pool. Usually the hardware reserves a chunk of the system memory for the iGPU.
Before Windows Vista, Windows apps normally didn't have framebuffers. There was one framebuffer for the whole screen, and apps drew into it. That's why dragging another window over a non-responsive window left a "slime trail" - the non-responsive window wasn't redrawing parts of itself when the window covering them moved away.