You are exactly correct. This is why you read several reports for the same action and get from them a consensus of what happened.
I, too, have been through dozens of order books, correspondence books and more at the National Archives and have noted that hundreds of items that should have been in the OR were left out, especially in the correspondence arena. This is also what is so disappointing with the OR Supplements in terms of what they COULD have put in them and what the left out and not just from the NA but also lots of other sources as well.
But, it is the best we have and we all lean on them for information.
Greg Biggs