I just tried it here and it works fine 
Sadly, on Windows, GUI apps does not have any stdout/stdin/cerr/cout/cin/cerr.
He should edit the .bat launch file in Notepad to launch with --console. He could do it by changing this line:
start “” “%~dp0\bin\synfigstudio.exe”
to
start “” “%~dp0\bin\synfigstudio.exe” --console