Since hundreds of people were involved the most likely explanation is incompetence
There is a lot of incompitence when it comes to file formats.
Though, makes me wonder if someone has intentionally sent out offers like that with lower numbers to make people think they're outsmarting them.
Don’t underestimate work shoved onto a university intern.
The most recent analogy I have is field techs in IT work. A company sends out "truck roll" tickets, and then complaints when there is a 40% failure/re-work rate on said truck rolls.
A single or handful of techs with said failure rate? Yep, perhaps incompetence.
A global failure rate across dozens of cities/countries and 40+ technicians total? No longer incompetence. At least at the field tech level. That's a documentation, process, and standards problem 100% guaranteed.
That some above average highly competent "hero" technicians are able to compensate for it is irrelevant.
If I have a sheet of paper and I color a section black. That's it. It's black. No going back.
So I can see people thinking the same for PDFs. I drew the black box. It's black. Done. They don't realize they aren't dealing with a 2D sheet of paper, but with effectively a 3D stack of papers. That they didn't draw a black box on the page, they drew a black box above the page over the area they wanted to obscure.
The fact that this happens a lot is an indication that the software is wrong in this case. It doesn't conform to user expectations.
You’re more likely to get at least one inept agent in a random sample of 1000 than a sample of 10.
I'm kinda surprised (and disappointed) nobody has done a Snowden on it though.
Hundreds of people might be involved, but the only key factor required for a single point of failure to propagate to the deliverable is lack of verification.
And God knows how the Trump administration is packed with inexperiente incompetents assigned to positions where they are way way over their head, and routinely commit the most basic mistakes.