Difficulty filtering timeline view

Like some similar threads, I've been having extreme difficulty in filtering the timeline view.

I manage a group responsible for roughly 20 active projects, with another 50 or 60 in the pipeline, all with varied duration and relevant to an array of departments and customers. Since I need to report these projects to other department heads, I took a tip from an old KB article and added a "Reported" checkbox to projects and folders, where I could optionally select the projects I want to export.

Unfortunately, this field is being flat out ignored when I filter on it. The timeline view is showing long since completed items whose "Reported" checkbox is unchecked. This creates a huge time sink, as I need to manually filter them out in Excel (including a plethora of internal projects that I don't want in the shared report).

I have yet to find a way to trim this down so that it's at all useful. Screenshot of this ignored field in action:

Help?