Hi Simon,
Concerning filtering by "Active", that is not a bug. "Active" stands for tasks that are currently being worked on, meaning with a timeslot running at that very moment.
Regarding the filtering, well, there is a filter that lets you selects a range of dates and show the tasks comprehended between those.
Have you tried it out yet? What about a Gantt Chart as well? Would that be useful?
Best,
Francisco