That might be the case with the Chunin exams, but Naruto and Team 7 have been sent on missions where they’ve combated fellow ninja and realistically would be required to kill enemy ninja, even if they avoid doing just that. True, Team 7’s first mission was a higher level than expected and they weren’t expected to necessarily fight trained ninja warriors, but it would have fallen on Kakashi’s shoulders to decide whether to let his Team to fight, possibly kill and/or die against Kaku and Zabuza.
Its probably the case where the First Hokage’s intentions for the Village and the actual result have been altered due to time, changes in the First Hokage’s principles and the influence of other people in this system. Perhaps the blog is slightly misleading, but the point is that children are still initiated to become ninja and soldiers for the Leaf Village long before they truly understand the dangers of combat and the consequences their career path can have on their lives.