APSCII

Not the most practical cameras, but the Sigma Quattro series (Dp & sd) flash sync in SFD multishot mode. Different than pixel shift, but similar end result.

It seems to me that this approach to combining adjacent groupings of same colour pixels would not increase colour accuracy per se (it would actually diminish it a little due to cross-talk) so much...

You raise an interesting point, but fail to appreciate that the results speak for themselves, and the results are excellent, when done properly.

The advantages are greatest for 35mm film for...

Because you retain some additional detail (above that rendered by a standard 12mp sensor) while achieving a similar level of noise. Additionally, you get the benefit of the much higher resolution...