I think I figured it out by accident, as usual.
When using a PDF conversion solution, I decided to convert to Form which means the OCR algorithm tries to identify the form and reconstruct it.
It generated layers similar to the one found by Hermitian but they are still active. I bet that importing them using paperport makes that functionality disappear, leaving ghosts.
I also venture to guess that I will find remnants of lines.
So far initial findings look interesting
Yes, it even uses a similar trick to hide the blocks and lines…
So much fun. So again, another myth bites the dust… Details to follow.