Because I have measured and weighed a lot of American terrier quarry over the years, I am not swayed in the slightest by the opinions of show ring matrons who have never cut five feet into a den pipe, nor do I place much value on the opinions of "one and done experts" or those who dig on their dogs only once or twice a year.
Similarly, I do not pay too much attention to those who barn hunt and shoot 20 raccoons in a day. Each to his own, I suppose, but by definition true terrier work involves moving earth and rock. I have done a lot of that over the years, and 20 raccoons was never part of the equation. Shooting 20 raccoons in a barn or silo is closer to shooting fish in a barrel than it is to terrier work. I am not trying to be critical, but I am trying to draw a distinction. True terrier work, by definition, involves dirt and a shovel.
As for those Americans who breed dogs for fantasy hunts in England, Scotland and Wales, I will leave them to their fantasy digging. I live in a reality-based world, and I do my digging on real quarry in real soil within 100 miles of my house. Terrier work is, by definition, not fantasy work. It looks suspiciously like digging on real dogs in real earth in the country in which you actually live.
As to "the standard" for any breed of working terrier, it was never written by a human, but always by the quarry being pursued. Because my terriers hunt, and because I value success in the field, I want a small terrier with a chest of around 14 inches or less -- the chest size of a red fox, adult groundhog or raccoon.
If you really want to understand what is needed in a working terrier, invest in a $5 fish scale from K-Mart, and a simple cloth tape measure available from any crafts store. Measure the chest size and weigh the quarry you are actually digging on in your area.
Measurement of quarry informs about the dogs, while exaggeration and fantasy is what deforms and results in the bully-headed, big-chested non-working dogs we find in the Kennel Club ring.
Before scales and tape measures.