You don't suppose Mapes typed up the documents based on Burkett's assumptions, and then gave them to Burkett to pass on ..?? I don't think Burkett would have the wherewithall to create the documents - although he does have a computer.
I think it is possible that Burkett manufactured the memos consistant with the questions Mapes asked him and overlooked the possibility that the use of a modern Word processor would give it away. There is no big wherewithall required for this, Just the standard MSword and an inkjet or laser printer. No big deal.