You'd normally compress the data before encrypting it as that makes the resulting cyphertext more resilient against cryptanalysis as well as reduces the amount of data which needs to be encrypted so this sounds like a bogus reason.
That doesn't allow you to deduplicate across users, though – which of course is the entire point, or the network would be able to see who's forwarding which documents.
It depends on what you're doing I guess... for storage it doesn't make sense, but for pushing a lot of data over a private pipe, why spend the resources adding a cipher?
