From what I understand, memory-in-pixel LCD technology is relatively new to the market. Does it rely on the same screen as “1980s” LCDs?

these aren't 1980s lcds, they have an order of magnitude better contrast (slightly better contrast than a swindle), reportedly an order of magnitude lower power (i haven't measured mine yet), and much lower latency

they do have glare but are quite readable in direct sunlight or outdoors in the shade or on a cloudy day

also they cost almost three orders of magnitude more

>in direct sunlight on a hot California day you can see a world of difference between the contrast and glare of a high school graphing calculator and a Kindle.

Sharp Memory LCDs are reflective, not transreflective. They're easier to read outdoors than indoors, much like eink. (Sharp markets these screens for devices like bike computers and gas pumps.) Some of the optical properties are in the same ballpark as eink as well.