I think it is interesting to consider the character of Jack when we discuss the character of Jimmy. Jack was a pure Season One LnC creation, and he has never been seen in any version of the "Supermanverse" before or since. What was Jack doing in Season One of LnC? I think he was being the kid. It's canon that there must be a kid in any superverse, and Michael Landes' Jimmy Olsen was unable to play that part. Therefore Jack was introduced. But after Justin Whalin took over as Jimmy there was no need for an extra kid, and Jack was dropped.
Ann