"Add Content Item" exposed filters only search panopoly_page nodes, despite changing "Content Type" filter

Steps to reproduce:
1) Base Panopoly installation with panopoly_demo and panopoly_article enabled
2) Create content type "Test" (any name will work, fields and other settings don't matter).
3) Add a "Test" node. For our purposes, title it "Test Node of Test Content Type". Other fields don't matter.
4) Go to homepage
5) Edit the page in IPE ("Customize this page")
6) "Add content item" to any region.
7) Begin typing "Test Node..." into "Piece of Content"

You'll immediately notice the error "The /Test/ return no results..."

8) If you switch the "Content Type" below "Piece of Content" to our "Test" content type, the right-hand preview will be updated with our recently-created test node.
9) Try searching in "Piece of Content" again for "Test..."

The error still is returned, despite searching under the correct content type.

Debugging:
Upon analyzing the Views SQL query for the "Panopoly General" view used by this add pane form, it seems that the content type "panopoly_page" is hardcoded into the query, preventing non-panopoly_page content types from being searched. The exposed content type filter seems to be totally broken.

The ideal functionality would be for the "Piece of Content" field to automatically search across all content types and then have the "Content Type" field assist in narrowing the search.