Exactly what makes a MOPAR a "Matching Numbers" car?

I think “matching numbers” applies to VIN stamped parts only. The rest is for high end restorations and doesn’t apply to the question. In my opinion.
I agree. The "matching" part of matching numbers refers to the vin codes matching. All the other parts are either correct or incorrect as far as date codes go, which means nothing since they can be swapped out.