Oh, it’s the same as others had. When the phone tried to boot after an update, it stopped at the encryption login, with no ability to type in the code. That’s why I was trying this fix.
I thought it was curious that it would have been a space issue, since I tried to be diligent about removing old versions when the phone gave me a warning that the space was low. But I thought that maybe one of the same files got corrupted, just by different means? But I wouldn’t know how else to check that.