Earlier quoted context omitted.
The refresh rate of eink is kind of...muddy. It depends on temperature and target contrast. With the right waveform and voltage, you can push it pretty far(like 30hz+). The thing is, Eink's waveform is kind of secret afaik, everyone has different tuning.
As I understand it going faster typically skips steps that are necessary for maintenance of the panel. Fine for a while but if you don't periodically run a "proper" cycle the panel could eventually be permanently damaged.
We had some secret eink sauce (propriety waveforms) to get the high refresh rates and colour contrast without a full flashing screen reset, but even then you need to run longer maintenance refreshes occasionally.
Pixels are just vertical columns of viscous fluid with charged ink particles. A waveform is just voltage changes over time to these columns to shift the particles up and down. More black to the top = darker shade of grey. Colour (in the gallery display, at least) is the same, just with each CMY particle group having different charges and responses to different waveforms.
Every once in awhile this vertical column gets messy with loose particles distributed through it (ghosting, muddy contrast) so performing a hard rail-to-rail voltage reset forces all the particles up and then down, and gives you a clean slate.