I think some birds do start with over preening and chewing, then move on to plucking. Some birds even rip their own flesh. Some birds will only chew and never pluck. Some birds will pluck and never rip flesh. All birds are different.
Honestly, he looks a little scruffy to me. How old is he? I'd be looking at things that have changed in the household, his diet, bathing, hours of sleep, exercise, toys, pets and people in the household, cage placement, time out of cage, schedule, etc. He might need something adjusted. He might be helped by having more to do. He could have a health issue contributing to it, too.