The Boxer breed standard specifically states that the Boxer should have a short, square muzzle. This is a defining characteristic of the breed. Any Boxer with a long snout would not be considered a purebred Boxer and likely wouldn't be eligible for dog shows or other events that require breed standards.
It's important to remember that breed standards are meant to preserve the unique physical characteristics of a breed. While there may be individual Boxers with slight variations in their muzzle length, a truly long snout would be a deviation from the breed standard.