package management - Why is the "Software" application not showing the same results as "Software Updates" or even apt?

I open the "Software" application, go to "Updates" and click the refresh button. The GUI shows this:

I open "Software Updater", let it refresh, and it shows:

On the command line:

~ • apt list --upgradable
Listing... Done
fsearch-trunk/artful 0.1+355+9~ubuntu17.10.1 amd64 [upgradable from: 0.1+354+9~ubuntu17.10.1]
google-chrome-stable/stable 65.0.3325.162-1 amd64 [upgradable from: 65.0.3325.146-1]

So... there are updates available. Searching for "FSearch" in the Software application shows no option to update:

The Software app also seems to be unable to find newer versions of repository software in PPAs or internal repositories. For example, even with the Virtualbox repository in my sources.list.d/, searching for "virtualbox" in Software only returns the package in the official repository, whereas:

~ • apt list virtualbox*
Listing... Done
virtualbox/artful 5.1.30-dfsg-1 amd64
virtualbox-5.1/unknown 5.1.34-121010~Ubuntu~zesty amd64
virtualbox-5.2/unknown 5.2.8-121009~Ubuntu~zesty amd64
virtualbox-dkms/artful,artful 5.1.30-dfsg-1 all
virtualbox-ext-pack/artful,artful 5.1.30-2 all
virtualbox-guest-additions-iso/artful,artful 5.1.30-1 all
virtualbox-guest-dkms/artful,artful 5.1.30-dfsg-1 all
virtualbox-guest-source/artful,artful 5.1.30-dfsg-1 all
virtualbox-guest-utils/artful 5.1.30-dfsg-1 amd64
virtualbox-guest-x11/artful 5.1.30-dfsg-1 amd64
virtualbox-qt/artful 5.1.30-dfsg-1 amd64
virtualbox-source/artful,artful 5.1.30-dfsg-1 all

Why? What is this app meant to do?