This is actually useful for smartphones. Sometimes smartphone malware is capable of infecting a device but not persisting, so reboots clean it back up.
Huh, interesting. I wanted to see how to enable this on iPhone, and the answer is that it’s built into iOS 18+ and will happen automatically after 3 days of no usage.
Yep, on GrapheneOS you can set it to a very short period (IIRC it is 10 minutes, don't have my phone here). Shorter timeframes than 3 days is useful in a lot of circumstances. I think in most scenarios where some agency uses Cellebrite or alike, they'll just make sure to do it immediately after confiscating a phone and not after three days.
It's another example of iOS security theater. It can be sold as "Apple cares about privacy", but it does not add that much meaningful security. (Just like: iMessage is end-to-end encrypted, but it doesn't really matter because most people don't enable ADP and only have iCloud Backups that are encrypted at rest.)
I remember something where on maybe mainstream Androids you'd have to fully turn off in order to turn it into BFU, but maybe it does just by restarting now.
You may be unfamiliar with its history. It was, for several years, a GrapheneOS feature. ("Magical" is up to the reader.) After much encouragement from the GOS team, Google, and separately Apple, implemented it years later.
GrapheneOS's implementation of it still remains the most robust. More info: