Is it possible that those 8 TB of data aren't actually data, but storage space - something similar to what happened in the case of CM? It might make sense that there is such a large amount of data, but why (and what) would a swap exchange store that takes up so much space?
Yes, the 8 TB is likely the total data cloned, as they probably performed a forensic copy, which clones the entire hard drive (bit-for-bit), including even the free space. All blockchains were probably included in that data. (How much space does just Ethereum take up?)