The executable alone is not the only variable in this game, but also which kind of commands GDB is asked to perform. And this is very likely different in a Qt Creator session to what you tried to in your manual session.
To see which GDB commands Qt Creator executes precisely, open Windows->Views->Debugger Log, and have a look at the left pane. You should be able to cut&paste that into a standalone gdb -i mi session, which I would not expect to react within 40 seconds either.