Sometimes symptoms of ADHD and developmental issues (e.g., impulsivity, short attention span) can be similar and, at a young age, it is difficult to discern if the child displays true ADHD or is displaying developmental issues which are not really ADHD. It sounds like the pediatrician is making a presumptive diagnosis of ADHD, but acknowledging the difficulty of making a firm diagnosis of ADHD in a child so young.
I'm not entirely sure what you are asking when you inquire about a possible relationship between Adderal and development. Perhaps you are asking if Adderal will be effective if your son's symptoms are deriving from developmental immaturity, rather than from ADHD. If he displays overactivity, the Adderal might be useful in either case. If he is displaying inattention or impulsivity, more than hyperactivity, the Adderal is not very likely to be of much use.
are teenage girls more mature than teenage boys?