Downscaled derivative images are what are checked, and if the reviewer even suspects that the downscaled image contains sexual content of a minor, they're required to report it. At that point, it is the authorities who decide whether or not to continue to investigate and determine if the user possesses CSAM. That investigation alone can ruin lives.
The "downscaled" image 360x360. It's pretty easy to compare two images at that size to determine if they are the same. You're not going to end up investigated unless you actually have actual picture of child pornography. Also, not just one, the process doesn't even start until you have a fairly large number.
It's highly unlikely that the apple reviewer will have access to the actual image in the database, instead they will assess whether the blurry,b/w,etc modified thumbnail could possibly be illegal. Given the level of secrecy surrounding the contents of the DB, even the normal NCMEC reviewers may not have access to those for comparison. There are plenty of CG images, small legal models, or even images of erotic toys which could be used as the base image which would look very suspicious as a low quality thumbnail.
> There will be someone along the line who will check that the image is, in fact, the actual listed image.
That someone will be law enforcement, and they will get a warrant for all of your electronic devices in order to determine if you actually have CSAM or not. It's literally their job to investigate whether crimes were committed or not. Those investigations alone can ruin lives, even more so if arrests are made based on the tips or suspicions.
