I can rattle a dozen examples off the top of my head of players who had that that short stocky fat build who were above average hitters. One was a player you mentioned, Rickey Henderson. There was also Joe Morgan, Pete Rose, Bill Madlock, Ron Cey, Steve Garvey, Kal Daniels, Kevin Mitchell, John Kruk, Matt Stairs, Tim Raines, and Gwynn and Puckett. All were under six feet tall, most weighed around 200 lbs, and most had short arms. It could be argued that the short arms led to more compact swings, and better bat control, and a more compact power base. All of those hitters had good plate coverage.