Software results are displayed in Shell Overview for already installed applications
This happens on both Fedora 36 with gnome-software-42.0-2.fc36.x86_64 and Fedora 35 with gnome-software-41.5-1.fc35.x86_64.
When searching for an application in GNOME Shell Overview, matching results from GNOME Software are displayed even for applications that are already installed and don't have another installation source (RPM or Flatpak). See the attached screenshots:
Both of these apps have only one source available and are installed from that source.