I had not considered that. I definitely "turn the page" much more than once every 15 minutes when I am reading on my ereader. When you take that into consideration, these Rdot screens are roughly 4 times as efficient AND have color as well.
I couldn't tell from the link but is it only tunable once to a certain chosen colour at manufacture time? Afaik EInk can achieve 3 states (eg, black white and red)
It's possible to do full-color e-ink in multiple ways, even if releases have been exceptionally slow.