From what I can tell it seems pretty hit or miss and it doesn't actually do anything with the information - no one tried to check my receipt when I triggered it.
When do they play this video? While you are in the middle of scanning items through the self-checkout or when you complete it? Is it accompanied by a frowny face or some other sign of disapproval to shame you?
After you bag the offending item. The video plays and a loud voice passive-aggressively reminds you to make sure you've scanned everything before bagging.