There have been people that have stolen from Walmart self checkout by acting like they are checking the items out through the register and scanning them.
But then they don't actually scan them and then place them in the bag.
But they did get caught and arrested for the theft so while it's possible to sometimes get away with the stealing from Walmart self checkout it's not worth it at all.
There are people that are watching the Walmart self checkouts and are alerted to any potential theft or if you're not scanning the items properly.
So it's harder now to steal from Walmart self checkout than it was before.