I agree with that, but in the specific case of AEDs it's hard to get something badly wrong to the extent that you actively harm: the main failure case is not doing something properly that could've been done. So you should definitely yield to someone who has better training, if available. But if there isn't such a person available, the AEDs thesmelves are completely automated and intended to be used by non-experts (experts use EDs that aren't fully automated): they sample the heart signal for several kinds of situations that can be corrected by defibrillation, and then apply the right one if detected. They won't fire at all if they're not placed correctly and/or if it isn't one of the situations where defibrillation would help, so you can't accidentally give someone the wrong kind of shock that makes the situation worse.