Two things make the crank set-up a possible improvement. One is reducing the weight from the awning which reduces the stresses on the mounting points as you drive. The internals really are heavy.
The other is it's possible (unlikely) for the awning to release while you are traveling down the road. Securing the arms will not prevent the roller from releasing, causing the awning to become a sail at 60 mph. Again, it's not likely for the roller to release on its own but there are stories out there where it has happened.
There are even devices sold to prevent roller release, essentially locking the spool from rotating. We just decided that the crank was a better solution and gives the same safety.