Good find Tom. I think you make a good argument for it being removed. But if you continue to the D2 section of the same document you will see numerous references to part numbers for a new partition. The page I posted earlier had a handwritten reference to "D2 modification" next to "3. Limousine Partition Glass". Here is a reference from the D2 section:
https://www.maryferrell.org/showDoc.html?docId=149138&search=westbay#relPageId=8&tab=page
If you read the beginning (pg2), the writer requesting these documents, Thomas Canning, complained that these all reflected pre-assassination modifications and not post-assassination changes about the trunk area, as he requested. All of this is about as clear as mud to me.
With there being No Doubt regarding the Officer Chaney Lead Car Event having occurred, I believe at this same time the JFK Limo was also Stopped. This stoppage being witnessed by Earl V. Brown of the DPD. With the SS having a locked and loaded AR-15 sitting at the ready on the floor board of the Queen Mary, I believe there was also weapon(s) inside the trunk of the JFK Limo. It would be foolish to believe that if the Queen Mary and the JFK Limo with the POTUS inside were separated for whatever reason, that the Only weapons inside the JFK Limo protecting the POTUS would be the 2 service revolvers carried by SA Kellerman & SA Greer. I believe when the JFK Limo stopped, the trunk was opened to retrieve whatever firepower was carried inside. With the assorted bric-a-brac connected to the Limo Top that was also piled into that trunk, retrieving weapon(s) amid extremely stressful conditions and time constraints made this a hazardous exercise to accomplish. I believe "changes" to the Limo trunk were a direct result of what transpired at some point between the Kill Shot and the JFK Limo arriving at Parkland Hospital. This is really what is behind the Thomas Canning question. There are Many Details concerning the assassination of JFK we still do Not know 54+ years later.