citing the 18-hour auto-reboot feature that returns the device to Before First Unlock (BFU) mode, where keys cannot be extracted.
Also worth mentioning that you can set auto-reboot to a shorter period (down to 10 minutes). So if you anticipate situations where your phone can be seized (border crossings, demonstrations), it's worth temporarily setting this to a short time period (or rebooting your phone yourself to get to BFU).
What about using decoy profiles? Say before the border crossing you switch to another user. Does that expose keys or anything for other users?
I dont understand why people like a journalist working on things they dont want seized would carry this kind of data on their device at a situation like this (border crossing), I see it as more useful to remove that kind of data from the device first.