VIN vs. Fisher body # on cowl tag correlation???

[JHS]

I heard from a guy who heard from a guy who..., well, you know, that GM VINs typically are within a 100 digit spread of the Fisher body number on the cowl tag, a possible way to make sure the cowl tag goes with the car. I compared these two numbers on my 67 Z28, 69 Impala SS, 70 Nova SS, 70 Camaro RS/SS and 68 Buick GS 400. Guess what? They all fell well within the 100 digit spread, the farthest off being 35! Has anyone else heard of this or am I just a novice late comer to the hobby? Is this a good way to verify a car's real cowl tag?