The old saying is a myth, of course. I don't know of any champion rifle or shotgun shooter who has only one gun. Same with arhery folks. Most competitive shooters will have at least one back-up bow, most have several. And all of them are always trying the latest, newest thing out there to improve their performance/scores.
Good shooters/shots are good shooters/shots. They'll hit what they're shooting at with any gun, rifle or bow you put in their hands. Nothing wrong with owning and shooting one bow, but that's not going to make you a good shot. Proper form, practice, dedication and inate ability are what does it.