It is true anyone can compare one case to another and move the die enough to push the shoulder back.
But that does not tell you the amount your new brass is going to stretch the first time it is fired.
It is not true, I am convinced most can not tell but there has to be a few reloaders besides myself that are very capable of deterring the length of the chamber before firing. A reloader should be able to measure the length of a case from the shoulder to the case head before firing.
Then there is that part about sizing a case and being able to determine if the case was returned to minimum length/full length sized before lowering the ram.
F. Guffey