they are looking for specific ones that are in a database

It could be any images, since there’s no signing of the hashes by CSAM organizations.

Its not like they can create a hash for a guy letting his dog on a horse

They could trivially create a hash for a specific picture of a guy letting his dog on a horse (which would also include other very similar images).

I didn’t necessarily mean to claim that they can scan for a concept lacking a fixed image, if that’s what you’re saying. That would theoretically be possible with enough hashes, but impractical.