What is the rationale behind potentially having an Access Services Manager I at a small, medium, or large library while only having an Access Services Manager II at a large library as presented on the Career Tracks draft document?

In the draft library staffing models, the Access Service Manager I position has fewer FTE (full-time equivalent positions, where 1 FTE = 40 hours per work week) direct reports than the Access Services Manager II does.  The distinction has to do with amount of direct reports rather than size of library.  Also, please note that the ASM I position is more entry level than the ASM II due to the number of direct reports.