Here's an IRC snippit which is my question:

Anyone done research on this?

I know I was a bit negative before, but I think I may have found something of interest. If you can access the Up/Down register (1 bit) and invert it, that should invert all the shifting behaviour. This means you would have to draw every other frame in reverse, but you would be able to cause said reverse at any point in the draw.

According to the datasheet, the command to set that register is UDE, which also sets whether you're looking at the X or Y direction. The code for it is:
D/I: 0
/WR: 0
DB7-3: 0
DB2: 1
DB1: 1=Y, 0=X
DB0: 1=UP, 0=DOWN

Also, from what I can tell the driver is intended for 128x64 displays. That tells me it's not half and half, but more like 3/4 updating the screen vs 1/4 not, and any extra is necessary driver overhead.

update: that command may not actually change the duty cycle, unfortunately. It looks like that might just be for the interface to the display memory, and the internal RAM is updated constantly at 1/64 duty cycle (or whatever the calc has it set to)

update 2: maybe try turning the display off. That might reset the shift circuitry beforehand, and if the on/off itself isn't too slow, it might be exactly what you're looking for.