What???
While you may list your assistant managerial position as employment, it IS leadership and it IS the kind of experience adcoms are looking for if you have an actual leadership role such as managing conflict, leading a team of your co-workers, developing strategies for improvement, etc. It doesn't matter if its at a job, a volunteer activity, or a club.
While the leadership tab may have been put on amcas to have an "easy" place for student organization involvement to go, it in NO WAY detracts from the fact that other experiences are indeed leadership.