1041405 to 1096404 equals exactly 55,000 US&S pistols, and the 55,000 pistols shipped is verified by US&S records. All the assigned block of serial numbers issued to US&S were used. The only time the complete block of 1911A1 serial numbers were not used was when the contracts were cancelled before the complete block was used.
Since some of the receivers and slides on the EXP pistols were P proofed they were not from initial set up, nor would they have had complete markings as some of the EXP pistols do. No one knows for sure what they are, but many being made from rejected or incomplete parts strongly suggest they were made up from the scrap box.
How another gun is serial numbered has nothing to do with how the 1911A1 was serial numbered. Colt serial numbered the slides for a brief period, but none of the other 1911A1 contractors did.