It's run as the system admin control of the windows installer on th "new" desktop, the same as other apps are from the automated script: SetupComplete.cmd
It's working find for other installers via the same script and the added switches are being passed on.. so the q is why is TC's install failing to either get (unlikely) or more likely failing to actually do as it is supposed to.
Example here is my current basic w7 install setup and the only part not working is the creation of icons for TC (desktop & SM.. which are fixed via a manual repair install after the fact but that really does not solve the problem):
@echo off
msiexec /i "%WINDIR%\Setup\Files\7z1700-x64.msi" /q INSTALLDIR="C:\Program Files\7-Zip"
"%WINDIR%\Setup\Files\BullzipPDFPrinter_7_1_0_1195.exe" /SP- /SILENT, /VERYSILENT /SUPPRESSMSGBOXES
"%WINDIR%\Setup\Files\Notepad PP 7.4.2 x64 silent installer.exe"
"%WINDIR%\Setup\Files\ChromeStandaloneSetup64.exe" /silent /install
"%WINDIR%\Setup\Files\Firefox Setup 54.0.1.exe" -ms
"%WINDIR%\Setup\Files\tcmd900ax32_64.exe" /A1D1G1M0K1
call "%WINDIR%\Setup\Files\killciep aka telemetry.bat"
dism.exe /Online /Add-Package /PackagePath:"%WINDIR%\Setup\Updates\windows6.1-kb2603229-x64.cab"
dism.exe /Online /Add-Package /PackagePath:"%WINDIR%\Setup\Updates\Windows6.1-KB2533552-x64.cab"
rd /q /s "%WINDIR%\Setup\Updates"
rd /q /s "%WINDIR%\Setup\Files"
del /q /f "%0"
Also.. no switch sadly for TC to add an icon to the quick launch or "pin to taskbar" .. but maybe in a future revision?

(it's as I've said many times my #1 used tool)