I can;t comment specifically on the Linux group, but in general you are absolutely correct. As a consultant, I see it daily in my practice. When I talk to people individually, they seem smart/knowledgeable, but as a group, they often make not-so-smart decisions.

That's exactly my point. It's not limited to the Linux core team. We divide into working groups of 2-3 people max to avoid this. Works quite well.

What does this comment even mean? What's wrong with them as a group?

To borrow a quote from a popular movie:

    A person is smart. People are dumb, panicky dangerous animals and you know it. Fifteen hundred years ago everybody knew the Earth was the center of the universe. Five hundred years ago, everybody knew the Earth was flat, and fifteen minutes ago, you knew that humans were alone on this planet. Imagine what you'll know tomorrow.

I think this is trying to say you are as strong as the weakest link? Maybe it's trying to say something about group think.

I mean all these movie quotes are all cool sounding but are quite shallow.

Answer: Yes.

Just because some thought has to go into the interpretation does't make it shallow.

A large group is often dumber than its weakest link.