Is there anywhere where you could actually try one of these out? If they worked as desired, I'd get one. A kindle updates so slowly I'm a little skeptical of the demonstration...
Kindles are not cutting-edge tech, they never were. They are robust and cheap, so they can enable Amazon’s strategy to flog at-cost low-end hardware that makes it easy for consumers to buy higher-margin digital goods. The likes of Dasung and reMarkable actually advance the field.
You can check some youtube test videos. But it's actually really that fast, I own Dasung monitors myself.