The Mozambique has a return to the guard after the two center body shots prior to transitioning to the head.
The Failure Drill was an LAPD adaptation of the Mozambique. It removed the return to the guard in favor of a direct transition to the head along with a two part assessment: 1- Is the head still there? 2- Is this person still a deadly force threat?
The above came directly from one of the two LAPD guys responsible for it.
If one is shooting two to the chest and then making the transition and head shot as fast as possible without the assessment, one is simply shooting two to the chest and one to the head and not a Failure Drill.