You're basically saying that those who worked daily in close interaction with the 10x developer and had to work with the code that developer produced, had lower regard for his technical ability than a manager who presumably is further removed?
You can't ignore the social aspect. A team with social frictions isn't going to work as well as a team that enjoys working together. Obviously just being social isn't enough but a strong team needs a combination of the social and technical aspects. Also 360 should mean going beyond the team, so the manager should be evaluated by his peers, his managers and his team and technical people on the team should be evaluated by members of other teams they work with.