You misunderstood the meaning of DefTerm!
The feature allows users to run children console applications in ConEmu automatically.
But you are talking about creation of console window in existing process / existing GUI application.
Your app was already started outside of ConEmu and perhaps created some visible windows, doesn't it?
It's started from devenv.exe, but when from inside ConEmu it doesn't open the console window, I guess due to the check (hOut == NULL). Still no output then :-( Yes, it first opens the GUI window. I'm asking because Issue#55 suggested the DefaultTerminal feature!
Today I got it working, the app had the console in ConEmu automatically, but strangely it stopped again. Not sure why, I updated ConEmu to 161009a and rebased the app as well. Now the default terminal appears again :-( Will have a look in Git.