Sounds like an engineer talking. I have always used my actual rifle to check fit. Industry standards are an average, rifles vary, sometimes because of lack of cleaning, sometimes just a difference in which barrel down the line to be bored out had a slightly worn out tool. Once you find the best grouping, exact duplication of everything done is the recipe. JMHOYes, throwing away a means to check cartridges versus an established industry specification in exchange for ammo that may only work in one gun and checking it is way harder... yeah that is a win. It is like throwing away the manual to your car because all those troubleshooting steps take too long.
If it doesnt fit the gage, there is an issue. Figure it out and actually know your process better. If it happens after seating a bullet then it is likely you have a diameter issue that a pair of calipers can detect. What is the pre and post neck diameter? Possible you have a neck thickness issue? A little math will tell, take some measurements and post them.