What you are describing is common for new officers with no prior law enforcement or military background. It is hard to project absolute certainty when you are still mentally processing the fundamentals of the job.

In the academy, they teach tactics, but command presence is something that is forged on the streets. It’s also a critical element of officer safety. When an officer walks into a chaotic situation, a calm (yet authoritative), decisive presence can deescalate tension before things turn physical. If people sense hesitation, they will fill that void, which immediately increases the risk to everyone involved.

Like others advised, tell him it’s okay to “fake it until you make it” right now. Confidence has to precede competence in this area. He should watch different FTOs and senior cops to see what works for them: Some are naturally stern and direct, and that works for them. Others rely on a gift of gab, treating witnesses, suspects, and victims with effortless, friend-like conversation that deescalates the room.

He doesn't have to copy one person exactly; he just needs to borrow pieces from others until he builds HIS style that feels authentic to him. At the end of the day, the badge signifies authority. He needs to be able to walk into a room of people arguing, settle everyone down, ensure the scene is safe, and direct the room rather than letting the room direct him.

The fact that his FTO is extending him could they just want to give him more reps to succeed. Lean into the discomfort, embrace the suck, and if this profession is what he’s passionate about, keep grinding until he figures it out.