D. J. Bernstein wrote:
The IETF shouldn't be sticking its nose into private
implementation decisions that don't cause interoperability problems.
But Rob Elz made a clear point in seemingly the only message you
*didn't* respond to that your implementation could cause
interoperability problems by potentially allowing for different contents
of the same zone with the same serial number. I won't regurgitate the
rest of his message, but it's in the archives.
If he's right (and it seems to me that he is), that's an indication for
either a standards clarification or a bug fix to your code, and maybe
both (indicated, IMHO).