Again bringing up Luffy is meaningless im this conversation. Brook felt more eager and willing to go by chapter 820 when they packed their bags. This was way after the debate on the way to nekomamushi, after the pekoms info dump chapter as well. Before that we got.... Him providing exposition of what happened and singing. Even before the facts were out, Nami was the only one who brought up the severity of the situation before pekoms. Chopper did this for one panel and peep from him until they left after the Jack attack on zunisha. And yes in zou it was about portraying how nami felt primarliy because as I said brook did zlitch in showing his willingness to go until chapter 820 (after the whole issue marinated for a while and nami and chopper decided to accompany Luffy). Chopper was reluctant to go in the first place as well, unlike Nami who had unwaivering determination to at least figure out what was going on