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

When the dash vin matches the title. The rest of the numbers don't mean a dam thing unless your selling it to a purist. You can change the rest of the numbers on the car easily. Some of them never came with body numbers and warranty engines don't have the vin.

There are more guys out there with Corvette engines then the amount of Corvettes made

Just my opinion, but to define “numbers matching” as ”the car is legal to sell” is too low of a bar. The VIN on the dash matching the title isn’t the only means to sell a car, but it’s not far off it.

No argument that the rest of the numbers aren’t really important unless selling it to someone that cares. Just saying that I think the “numbers matching” tag should mean more than what a shell with a dash and VIN tag has.

Edit - I should add that I understand that you are saying the numbers beyond what is needed to be legal are pointless to you. Completely get it. And not disagreeing, other than in reference to how I would define “numbers matching”.