I have a question regarding two-year-olds and Thoro-graph figures based on their foaling months.

For example, lets say you have two horses, one foaled in mid-january and the other in mid-april. They both make their debuts in early August and each runs a "15" which is a true representation of their ability at this time in their careers. Just for this question, everything else will be constant -- similar breeding, similar trainers, etc. So my question is, if they run the same figure in their first start, would you eventually (in the coming months or years) expect the younger horse (the one foaled in mid-april) to be faster? If so, is it significant -- in other words, do the horses that are born two or three months earlier have a significant advantage early in their careers?