i've seen no evidence that training can change the shape of your muscles.
i agree with the premise that the shape can change once you've actualized your genetic potential ie the muscle fills out. also condition can affect the appearance ie more definition = more peak. pumpster is correct when he says too many people concede limitations before potential, but shape is genetic.
consider, for eg, how arnold had a much greater peak on his right bi than left, yet he trained both bis with the same exercises, sets, reps, weights, etc.
it wouldn't matter how many concentration curls sergio, hawk or levrone did, they would NEVER develop a peak like beckles or robby. conversely, beckles would never get the fullness of sergio.
wouldn't matter if franco lived on the preacher bench, he is never getting the fullness of scott.