Manage your project with your developers

I have read Udi Dahan's post on letting someone other than developers manage the project, and disagree with him on several points.

Udi starts by stating "Developers don’t know how to estimate".
He than "backs it up" with the explanation of the fallacy of an estimation to the distant future:
"For example, if the estimate is a day, you can expect it to be finished in around a day. If the estimate is a week (5 works days), it will probably vary between 4-10 work days. If the estimate is a month, in all actuality the developer probably doesn’t know enough to say but will answer when pressed."

He than suggest this approach: "The difference is that by working based on features, and measuring project progress by feature-units completed per iteration, I drive down variability"

Sounds Agile to me.
But I fail to see where does "don't let developers manage the project" fit in this statement.
If you work using an Agile methodology, you make estimates based on small units of work, and are able to adjust the course of the project as you go along. This has everything to do with methodology, and nothing to do with the qualifications of the person managing the project.

There may be reasons for not letting developers manage projects, but this is not one of them.