If I recall they made it through the Forest of Death in about 2hours(might be off). That right there should already tell you how much more advanced they were compared to the leaf genins. The examiners even realized they were beyond gennin level ninja. They also made it to the finals during the chunnin exam. Hell look how much they improved when they went up against the sound 5. Dude I could go. Its very possible for them to advance the way they did what the time that passed.