When using my reader, sometimes mutations require a full screen invert. Sometimes stuff just seems to change trivially. What governs that? Is that done by the display or driver or higher level code?
The problem with e-ink is that redrawing pixels without cycling leads to ghosting after a few draws. Most displays automatically cycles the entire screen now and then to mitigate this. I guess it's up to software or firmware to detect when to do it.
The Waveshare displays do support partial refresh, but I haven't had time to look into exposing it into Node, yet.