In the US puppies as young as 3 months can compete in matches (practice dog shows - no points, just for fun and practice). With a show potential puppy, training begins from the time it gets home, but training is done as playtime and games are made. It is not unlike many of you who begin training your puppies for basic manners. Puppies get set up on tables, even fed on the tables to get them used to being up there, teach them there is nothing to fear and fun stuff happens on the table. (Also useful when taken into the vet for an exam.) Feet are played with (helps with doing toe nails), teeth are looked at (also useful during vet exams). Leash training begins, not in a forced heel - heeling is not natural gaiting for a corgi and that's what a judge needs to see, but then you leash train puppies and teach them to walk on a loose lead (hopefully

) too. Handling classes are where they get to socialize and be with other dogs, meet new people and get adored by everyone (not unlike basic obedience classes). Baiting - (watch me command in obedience classes) what corgi doesn't go for the food and helps teach a free stack.
In AKC at least, puppies cannot compete until they are at least 6 months of age and then they can earn points towards their championships. I don't really get the logic of the NZ KC's decision as the awarding of CC's is much different than the point system of AKC.
Even at 6 months, judges do allow for puppy antics in the ring and they are forgiven. So it is anthromorphosizing to equate puppies being shown to childhood beauty pagents.
My next puppy will probably be herding instinct tested at around 3 months of age. I'm also thinking of taking her to puppy headstart, as much for me as for her.
Just because it is training and working one's dog, doesn't mean it can't be fun and playful. Although I do agree I'm not sure a 3 month old puppy has any place in a show other than for the fun of practice.
Debbie