To my untrained eyes I can easily see when the lines are not exactly the same, so for a master carver he surely can see that as well. About what we're seeing what it seems they can't just make a perfect copy, this is just speculation from my part as I'm not familiar with their circumstances.
I can imagine the guys that are in charge of making knights, they're restraint in time and materials (in particular expensive/exotic woods) and the boss probably doesn't care if it's not 100% exact, 90% is probably good enough for him as long he gets his knights in time ready. The tools are probably old and not regularly maintained or replaced.
I personally think if a master carver is given carte blanche time and materials wise, he can make an exact copy.
I'll say it again, this is just speculations from my part.
My experience with Jaques sets is that the quality is still very good. Yes, they are made in India, but the quality of carving, fit of weighting, finish is better than most reproductions. I understand that Camaratta is the engineer behind the modern Jaques sets, and I expect his high end reproductions are as well (better?) made. However, the lower end HOS reproductions are not as fine as the expensive ones.
The antique Jaques set are artfully carved, and it seems to be difficult to copy those lines exactly. I have a circa 1895 "Marshall" set that is fabulous, but the weights are lighter than today's reproductions, bases are not identical from pawn to pawn, bishop to bishop, etc., and the white boxwood pieces weigh less than the ebony black ones. But, it's a piece of art. Craftsmen today and then were artists. Well made reproductions today are beautiful in their own right. So, I don't think the value of Jaques or House of Staunton is all in a name.