Most refresh times that are listed are for "full" refreshes, not specific state-to-state timings, specific color transitions can be MUCH faster. This is how the reMarkable achieves its low latency drawing (around 21ms for white to black), which it can do for the whole screen, not just a sub-section. Other specific shade transitions can also be quick, it depends on the details. But it's more than fast enough for typing purposes, your current keyboard-to-display latency stands a decent chance of being higher.
The tradeoff is that continually doing those faster transitions gradually accumulates errors, i.e. ghosting. Which is why e-readers tend to do a few pages of fast changes, then do a full refresh to clear things out (or before/after an image is shown). Fast-transition latency beyond something like 50-100ms from button-press to page-turn nowadays is almost exclusively due to software on the device, not the screen.
The tradeoff is that continually doing those faster transitions gradually accumulates errors, i.e. ghosting. Which is why e-readers tend to do a few pages of fast changes, then do a full refresh to clear things out (or before/after an image is shown). Fast-transition latency beyond something like 50-100ms from button-press to page-turn nowadays is almost exclusively due to software on the device, not the screen.