There is some confusion about the definition of a link. A link is only 1/2 inch. If you use the big/big method, you add 2 links or 1-inch to the length, after the ends are brought together. If the ends that come together are the same, they can't be joined and 3 links should be added.

I recommend the little/little method, particularly when you are using a cassette with the standard size largest-cog sold by Shimano for a road bike. With the chain installed through the RD it should be as long as possible in the little/little combo. If it's not hanging loose or rubbing the upper chain guide tab on the RD, it is not too long. When the ends of the chain are brought together, the lower pulley should swing down slightly, indicating that tension is being applied.

If your chain is really too long, it would hang loose in the little ring and several of the smallest cogs. If it never hangs loose or rubs the RD it is not too long.

There may be some difference in how a Shimano RD reacts to this situation, but with a Campy RD, the upper pulley just gets closer to the largest cog if you shorten the chain.

What is being overlooked here is that the RD hanger is not necessarily the same on all frames and neither is the stop that the B screw rests against. You may simply need a longer screw to compensate for an error in the frame.