[William Sommerwerck]

You need to go and have a bit of a think about this. The number
is directly proportional to the pit length. So whether the pit length
represents a number, which in turn represents a voltage, or
represents the voltage directly, the same length errors have the
same final voltage effect.

Not if the length is quantized. It can vary (within limits) and still be
correctly read. This is not true of analog.