I hear that a lot also, but what I don't get (and I don't do lugs for the most part) is what the heck they are talking about. Don't most tubes normally just penetrate the lug and get trimmed "roughly" off. With the exception of the top tube to seat tube. You can have head tube lugs that meet the head tube at a tube, though some simply penetrate the tube also, but you still have four other joints that are just pass throughs.

Now if you want to see tight mitres the TIG guys will make your day, they tend to use machinery and cut to very tight tolerances, though any builder can do that whether it helps or not.