It was a scam because the 970 cards were advertised as featuring 4GB of memory that runs at a specified bandwidth, but the final segment does not meet this specification. This has been shown to impact Blender rendering, where (when scene complexity spills into the slow region of memory), the 970 loses out to older cards that it shouldn't in rendering speed. You ordered a video card with 4GB of 256-bit memory at whatever specified bandwidth, so that's exactly what you should be getting. If we let NVidia cut corners like this, things will only get worse.
As far as dual GPUs on one board and memory usage, I'm not experienced with this type of card, but in theory, you could run a game on one GPU and use the other GPU to do Blender rendering or be the graphics head to a Qemu or something, at which point you could actually make use of the full 12 GB of the dual GPUs, since game data isn't duplicated between them and they're doing separate tasks.
But nothing you do to a GTX970 will make it perform like a real 4GB card. And if people knew what they were getting with the 970 wasn't really 4GB of 256-bit memory, they would have probably chosen a different product. Video memory is important, and it only becomes more and more so as the card ages. Once games really start to tax 4GB cards, this will become more of an issue.