There are plenty of examples of a single set of documents with no corroborating documents. In fact, when I was a lawyer for Lehman in 2008 most mortgage transfers were a line in a spreadsheet not a legal document. Many wills have only a single copy that was kept in a safe deposit box. I could go on and on.
The fact remains that altering a photocopied or faxed copy of a document has been trivially easy for decades and yet it's not really a problem in real life, because it's a criminal act to do so and present it as authentic.
Which is easier to do this 10,000 times a print and scan work flow or a python script that calls this library :).
I own home care agencies in 13 states and in the early years had to collect timesheets with physical signatures for medical billing. I know the work involved in printing, collecting, scanning, organizing and retaining/archiving physical signatures at scale. We lost real money when signatures weren’t collected or were lost because there were times we couldn’t collect a replacement for various reasons.
I then built the digital system to collect signatures and had to get legislation passed to make them legally valid. We were literally blocked for several years because digital signatures were not permitted. So this isn’t a hypothetical I am throwing out just to make an argument and be annoying.