The canonical Boolean values in FORTH are 0 and -1 (that is, all bits set). IIRC the point of that is to unify the bitwise and logical operators, though, not detect bitflips.

Also, at the machine code level, a Boolean controlling a branch or a while loop often doesn't ever make it out of the flags register, where it'll only be a single bit anyway because that's how the hardware works. Not really changeable in software.