Nope, not "always".

Yes, it will (almost always) fix the example given for 'symmetric change' (I think he called it)

But, it is a hash - so there are collisions.

A hash on a table that could contain millions of rows and a couple hundred columns is condensed (hashed) down to a single scalar value which is the hash value. So, logically there are some hash values that have more than one source.

(There are hashes which are 'perfect hashes' but those are restricted to a specific set of data and the source data must be known in advance. Not possible in this discussion)

HTH,

-Chris C.