
That is how Good citizen and the other breed classes are judged.
The only difference in Good citizen class to open is that they have to have a Good citizen qualification.
Both my Good citizen dogs are veterans (haven't bothered to get it for the younger ones) so I rarely enter them in more than one breed class as second entries are now so expensive and I like to ente4r veteran stakes if I'm going to enter more classes.
When they were young I would enter both another breed class and Good Citizen.
Actually at Crufts where second entries are free I have entered my 10 year old in Open, and veteran, but forgot to do Good Citizen, duh!
It is also useful if you have two dogs that can only go in Open to use the Good citizen class, assuming you have got the qualification.