Take a look at Rafael Nadal- his left arm is a lot bigger than his right. Most of the top tennis players have imbalances when it comes to their dominant v non-dominant arms. This is not unusual.
Ryan is young enough that he can put on a good 15-20 lbs of muscle in a year without the aid of anything chemical. From the time I turned 16, and started to lift, to the time I turned 19, I put on 30 pounds of muscle, and never even looked at a needle. His face is a lot fuller, which tells me he's eating a lot more, working out heavy, and not doing a ton of cardio.
And for those of you who want to compare him to little PDW, a power player like Ryan is always going to look for ways to increase his power, and short of throwing it two handed, hitting the gym is the best way I know how. Having agility and motor skills are nice, and are the foundation of a bowler's game, but when you can add brute force to your existing gifts, you can be dangerous.
Good for him- when Tiger hit the PGA tour, and his arms were starting to stretch the sleeves of his shirt, more and more guys followed him to the gym to keep up with him.
WITH ALL OTHER FACTORS BEING EQUAL, a good big man will almost always beat a good small man. That holds true in just about every sport there is. Unfortunately, all other factors are never equal, especially in bowling. Being in good physical condition, which includes being stronger, is definitely an advantage in bowling, though. There are a lot more Chris Barnes body types than Dale Trabers at the top of the money list.
Experience is something you get immediately after you need it most
Bowl up a Storm!