I think your Kindle use case is single device but mine is across 4 devices so doing anything fully locally doesn’t really work. Unless each device would need to be trained.
> don't we also have to factor in possible different text sizes on these devices, too?
The kindle tracks progress via the actual amount of text read instead of pages, so the screen and text size should be irrelevant. It can still be switched to display the page number, but that is also independent of the amount of text on the screen(meaning it doesn't necessarily increase with every swipe to the next "page").
>The kindle tracks progress via the actual amount of text read instead of pages
This doesn't seem to me like what the tweet is describing, wherein the kindle is registering every tap instead of distinct "x words/chars progress made".
If they were capturing and storing "X words in fiction read in n seconds", I could understand it, but they're not: they're registering every tap.
I'd be interested to see how this matches up with "userChangedTextSizeToBlah" data if this is how they're calculating reading speed.
Also, slightly OT: has Amazon ever said whether that reading time is calculated locally or on their servers?