The threat model is "antagonist creates colliding image which is CP, claims original unviewable file was CP."

So you, the protagonist, have an encrypted volume full of the names and addresses of people helping evacuate Jews from Nazi-controlled Europe / blockade the construction of a new mine which was approved through bribery and corruption. The antagonist claims you are a CPer and produces a list of known hashes on files on your disk, and a sample of really awful images that conveniently have the same hashes.

So the end game is either bust your information out to assist prosecution of the anti-government activists, or land you in the slammer as a CPer thus dragging your cause into the mud.