Oh, it's definitely a programmed thing -- iRex refers to it as the refresh "waveform," I think. And the aim is, indeed, just as you suggest: to reduce ghosting. The iLiad may be able to get away without it since they've got a bit more 'developed' display. And as I recall, there was actually quite a bit of debate (we caught faint echoes of it) about jsut what sort of waveform was the best to use.
As I recall, alex_d had come up with a 'flash to
white' approach that worked fairly well, with only slightly increased ghosting as the trade-off.
I hadn't realized that the iLiad didn't do the "flash to black" anymore, the last time I saw one (early last summer), it did the same refresh the Sony does.