Cant be real. The slide does not retract at all upon firing.
Primed case only in that test, not a full round.
The video uses a blank with only a primer, not powder or bullet, so there is no pressure to force the empty cartridge and slide back. The test was just to see if the safety could be defeated, and it was with the right number of drops and angle of the drops.
The persons doing the test already knew about the safety issue, the video was to demonstrate what circumstances would cause the misfire, so they used blanks as the others have mentioned.
Yeah. They drop test with live rounds?
Primer only.