isn't it for the kids?

I have a short rant, and maybe I am totally wrong here. N. has been working on his Pinewood Derby car for Cub Scouts. This is his first year to do all this scouting stuff. He is so very excited and has been working hard. He is so proud. Isn't that what it is supposed to be about? I took him to a practice run with his car... and guess what?...Some of the cars looked like they could never have been totally done by a boy of this age group. You know why? Because they probably weren't!! I am so disappointed and I hope I am wrong!! Please tell me I've made a miscall. I'll bet that the majority of the boys were allowed to do their own work along the whole process but still I couldn't shake the feeling that some of the cars seemed 99% completed by someone over the age of elementary school!!!!
I hate that N., in his naivety, feels less talented to do that kind of work. I tried to explain that those cars were probably not really done totally by a young boy. I hope I am wrong. I believe
kids need activities that don't involve a grown up "fixing" everything.