First, different shows have different rules
4-h do not follow APA book of Standards, for example a common 4h project here is, they give out 25 chicks to kids, at the end of 6 months , I think it is, they show them. The breeds used are one of the commercial variety, like Tyson 125 .
County fairs - quite frankly , I am not sure what standard our county fair go by, Last year the rooster that won, was handsome indeed, but didn't fit come close to fitting the Brown Leghorn standard.
APA - shows - many of these shows will allow APA recognized breeds , with non-approved standards. While they will not be able to send their points in to the APA, the shower can still win best in breed or best in variety. I know , I use to bring my BLRW to shows. They are judged on the overall breed qualities.
I personally believe thats the best way to get new varieties accepted (as long as the breeding rules are valid).