In the 50s and into the 60s, there was not that much distinguishing the shooting guard from the point guard. Maybe one guy handled the ball a bit more than the other, but in general players were just "guards" and their roles were fairly interchangeable. In the late-50s/early 60s, as the game continuned to evolve, positions became more defined and a new type of player emerged. These players were taller, like forwards, but they didn't rebound and bang down low, like most forwards. Instead they specialized in shooting and scoring. At that time, scoring was almost entirely done by forwards and centers; maybe someone like Cousy was an exception, but the biggest scorers in the game were either big men (Mikan, Pettit, Chamberlain, etc.) or forwards (Arizin, Fulks, Schayes, etc.)
The new guards didn't distribute, they were all about scoring. Sam Jones (and Hal Greer) would be the protoypes for generations of scoring guards who would come into the league and get buckets. Lanky, athletic, guys with sweet strokes who started mastering the art of shooting, something that really hadn't been developed in basketball up until that point in time. Creative and aggressive, Jones was capable of scoring in multiple varietys, from an array of different types of shots from all angles over the court, as well as someone that could penetrate and finish around the basket. Years ahead of his time before the three point shot was developed, Jones was a sharpshooter who also stretched defenses to new dimensions, which opened up holes for teammates like Cousy and Havlicek to operate.
Sam didn't start until he was 28 years old, stuck behind Bill Sharman. His best season would be in 64-65; Cousy had retired the season before and the Celtics were missing their engine on offense. Havlicek was good but not quite JOHN HAVLICEK yet. It was Jones, who averaged 25 ppg in the regular season and 28 ppg in the playoffs, who guided the Celticcs to the title that season.