The correct statement SHOULD be, shooters are more accurate with longer bows, than short ones. The longer bows are more forgiving of mistakes.
When I used to shoot compounds all the time I bought a High Country twin cam bow. Everyone told me, "it will be the most frustrating, inaccurate bow you ever owned, because it has twin cams AND it's short. By the way it was longer than MANY of the newest compounds on sale now.
I used that bow in a couple dozen competitions we held there, and I kicked the butt of every one of the folks that warned me away from that bow. On one shoot, we held was a 2 man team shoot. My teammate was a former pro shooter, and he and I traded top scores for our team. He always shot his target bow.
It's not the bow, it the shooter. But short bows are demanding of perfect form.