Ah. I didn't think of that because usually you have to unlock the bootloader to do that, which on most phones also wipe them, void the warranty, and often leave some kind of marker that would be obvious. But it depends on the phone still. And it's not uncommon for those things to be disabled on updates too. Also, Samsungs don't have fastboot at all, so that wouldn't be an option for any of them.
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