I'd have failed too, because I use a very particular way to describe a hashing function.

A hashing function is actually a sorting function. It's supposed to take an input space and sort it in an unpredictable and evenly distributed way across the output space. What's more, neighboring points in the input space, no matter the sort used to determine proximity should not result in neighboring points in the output space.

Fingerprinting is just an emergent value that comes from choosing fixed length hashes, and the fact that the mapping from input to output is stable.