When ancient black smiths made iron they tried to make it as clean as possible. They hammered and fold iron over and over again until there were no dross. Outcome was clean iron, but after some time they noticed it was not strong enough. They realized that making something as clean and homogeneous as possible does not make it strong.
Then steel was found. As we know iron becomes steel when there is correct amount of carbon inside it. Iron is not clean because there is carbon, but without it there won't be steel. In that sense certain weakness makes iron to steel. If the phenomenon is looked from the physics point of view, carbon atoms find their places between iron atoms and this makes structure strong.
Same idea can be put into team building and collaboration. There are team members with different backgrounds and competencies. Instead of trying to make them look the same and have the same competencies, hammering and folding over and over again, there should be paid attention to competencies and how those competencies are fulfilling each others. When team knows what are the pros and cons of each of others they can backup each others. This makes structure strong as steel.
Why this makes team strong? Think about the case when everybody is just showing their best sides and hiding bad sides. Most likely at the end of the day team does not look like a team but just a bunch of individuals. They do not know each others, their pros are not supporting their cons. Such a team might be iron but not steel.
