Thats entirely different, and its a dumb argument to make. ATI doesnt support it, period. Yeah, someone may be able to make a hacked driver for it, but the limitation is likely in the hardware.
Its like saying we can SLI a GTX 280 with a GTX 480 if we try really hard. In all likely hood, its just psychically impossible, and pointless to do.
They said we couldnt go to the moon. Does that mean we can go to Uranus? No.
There are some things in life that just arent possible.