They are not the same thing, but when you boil it down to the raw math, they aren't identical twins, but they're absolutely fraternal twins.
Both are trying to eliminate repeating data, it's just the frame of reference that changes. Compression in this context is operating on a given block or handful of blocks. Deduplication is operating on the entire "volume" of data. "Volume" having a different meaning depending on the filesystem/storage array in question.
Well put. I like to say compression is just short range dedupe. Hash based dedupe wouldn't be needed if you could just to real-time LZMA on all of the data on a storage array but that just isn't feasible and hash-based dedupe is a very effective compromise.
Is "paternal twins" a linguistic borrowing of some sort? It seems a relatively novel form of what I've mostly seen referred to as monozygotic / 'identical' twins. Searching for some kind of semi-canonical confirmation of its widespread use turns up one, maybe two articles where it's treated as an orthodox term, and at least an equal number of discussions admonishing its use.
If anything I would expect the term “maternal” twin to be used as whether or not a twin is monozygotic or “identical” depends on the amount of eggs from the mother.
Both are trying to eliminate repeating data, it's just the frame of reference that changes. Compression in this context is operating on a given block or handful of blocks. Deduplication is operating on the entire "volume" of data. "Volume" having a different meaning depending on the filesystem/storage array in question.