Do you mean like you can't just add a 256-bit bus on gf104?
What?

GF104 has 4 memory controllers, one is disabled to give 192-bit on the 768MB version, all 4 are enabled on the 1GB version.
Considering GF106 is basically supposed to be half a GF104, it would be weird if they had 4 memory controllers and disabled 2, and even weirder if they had 3 and disabled one on the only card being made at the moment with that core.
I'm not quite sure what point your comment was trying to make.