Have a documents content type, with three taxonomies applied to it. Taxonomies are document type (form, policy, other), document group (hr, i.t., training, project specific, etc.), and a free-tagged project name (for when document group = project specific).
Have single view displaying all documents, segregated by tabbed page displays:
Exposed Filter on individual pages:
Now that we have the project specific page/tab, we want to remove 'project specific docs' taxonomy term from the Forms and Policy page/tabs dropdown filter on just those two views page displays. It's already filtered out, so if you select Project Specific Docs on those pages you get no results. Just need to remove the option from the select list.
UPDATE: found my own answer
4 hours later, realized I've been overthinking this. In the exposed filter there is a simple checkbox to "Limit list to selected items, If checked, the only items presented to the user will be the ones selected here." Derrrr. And it is per display page.