I edited this post to clarify the problem and include the solution. You can ignore the 2 posts below. Problem:
Unable to get the Windows Features Control Panel to populate when launching it directly using the following rundll32.exe command:
rundll32.exe shell32.dll,Control_RunDLL appwiz.cpl,,2Solution:
After a bunch of testing it appears the problem is in rundll32.exe itself. Populating the list of features is actually done by TrustedInstaller.exe which can only be run by the built-in System account. System fails to create the svchost.exe process to do this if rundll32.exe is launched by any process besides explorer.exe (via the Run dialog) or cmd.exe (directly from the command prompt). I ran into the same problem attempting to launch it indirectly from the command prompt using NirCmd's exec feature.
As an alternative it can be launched using the built-in alias of optionalfeatures. Technically it's optionalfeatures.exe, but it only seems to work in LBC if I leave off the .exe file extension and doesn't even work with that syntax when launching via NirCmd exec.