I believe that all the known unaddressed 10:00 AM covers are Worden covers. I also believe that a significant number of such covers were addressed at a later time when they were either typewritten to Worden or to a customer. There is no evidence that all Worden covers were initially unaddressed.
Worden probably had some inside help in preparing his 10:00 AM covers. This could account for the unaddressed covers. It is no secret that Worden and Superintendent of Stamps Michael Eidsness had a good relationship. For example, when the new Special Delivery stamp (Scott E12) was released earlier in the year, Eidsness apparently sent a FDC to Worden with an enclosed letter certifying that the cover was indeed a FDC. There is some evidence that the cover and letter may have been backdated. They are part of the Peltz Special Delivery collection housed in the John Hay Library at Brown University in Providence, RI.
The Philatelic Stamp Agency did report to Eidsness.