Date range for visitors-list type

Hello,

So far working with the API has been pretty intuitive. However, I've recently encountered a puzzling problem I can't figure out. When I use the visitors-list type, it only displays the past 7 days worth regardless of the date range I explicitly request. The date ranges work for any other type I choose, it just seems to be the visitors-list where it becomes limited. Why would this be? Is visitors-list only available for the past 7 days?

Thank you,
-Dave