On kindle, if you tap the middle of the screen, then click the little Aa up top, you get formatting options. On reflowable formats, you can go to the more tab and uncheck the animation button. On ones that are fixed pages, it should be one of the only options.
I could see the benefit on a non-phone mobile device. Completely cutting power as a deep sleep without needing a lengthy boot sequence could be nice.
Unless it’s actually “just as fast” as volatile memory (including progress to the latter) and not more expensive, though, it seems like it wouldn’t justify the tradeoffs.