Agent Larry Carr....
If your willing to accept that these individuals were not able to obtain basic physical identifiers for Cooper then he could have been of any race, any height and any weight. The description came from many who saw him, not just Schaffner and Mucklow. Several passengers sat near Cooper and noticed him because of his actions. They reported a physical description of Cooper as Schaffner and Mucklow. As did the ticket agent in Portland.
Under the "trust no I-witness" philosophy, there is no base of fact to go from, maybe he was actually a she? Where do you stop? there has to be a baseline of fact, you simply cannot conduct an effective investigation if every human being is a suspect
There is the key difference, "it happened so fast" Not the same in the Cooper case. Mucklow spent almost five hours with Cooper, I think she could have got the base physical indentifiers correct, especially when the others reported almost the same.