There are a number issues which potentially contribute to eye strain: Staring into a lighted display. High blue spectrum of the light. PWM. Dithering.
None of these factors are an issue with e-ink. We know that current display tech is giving us eye strain and harming our vision. But no manufacturers (other than Dasung) are addressing the issue. Year after year they continue to pump out the latest and greatest displays and devices using led display tech, knowing that led displays are causing many people eye discomfort, strain, and health issues.
So what can we do? Dasung is doing it now, but since none of the major companies are adopting e-ink tech for text displays, fast refresh e-ink displays can't reach a mass production price point which would make them practical and affordable for the majority.