Yes you can indeed fail for this, I have seen it myself this week. None of the load securing devices are difficult and your trainer should make sure that you are competent with each device. Get ya hands dirty and get stuck in, make sure you know how they all work.
You need at least 15% on each section and an overall score of at least 80% to pass.
So the scenario is that you show where on the vehicle you would place the load =5%
Explain what restraining device you would use =5%
Show how to secure using said device =5%
Show how to remove said device =5%
You cannot show how to correctly remove the device if you have not secured it in the first place . This results in a fail .