Nozzle-less motors are practical for mixtures that don't chuff easily and have a fairly high burn rate. A longer core is needed for such motors.
The coring rod should leave around one diameter of un-cored propellant at the forward end to hold pressure. I didn't watch the whole video to see whether that was done.
The sad thing isn't that this guy may win a Darwin. It's that impressionable youngsters will look at that and think "Hey, it looks easy, let's try it!" If they're lucky they'll merely have to explain the huge cloud of smoke throughout the house, and the burn marks on the kitchen ceiling. **IF** they're lucky...otherwise