Right. So why does the fact that they targeted 34,500 ports show it was a well-engineered attack? By itself it's just evidence that they know how to iterate over ports. Coupled with the data size (7.3Tbps) we know they had an enormous botnet. None of this points to a well-engineered attack, it just means that lousy IoT has made botnets incredibly cheap.

A well-engineered attack would not draw headlines for its scale because it would take down its target without breaking any records.