"This will show any assets that are identified as "Installed, payware"."
Even in a base installation some assets are marked as payware.
The only guaranteed way of determining if all dependencies are either built-in or from the Download Station is to have a fresh, clean installation of TRS19. Import your route or session into this installation and then right click and select Download. If you end up with missing dependencies ... .
Another complication are the four additional free routes that come with TRS19 but have to be selected and downloaded. Some may choose to install these; some not.
Of course you might decide, as many seem to do, that having only dependencies that are built-in or from the Download Station is not important. Then you can either leave it to the downloader to identify and find the missing dependencies, or you can provide links (assuming you know where they came from).
As for this standard required, you just have to look at some of the material on the Download Station and draw your own conclusions.
Phil