It also appears that it doesn't copy the whole file upon changing one of the files. It only stores the changed portion. I assume this is block level. Pretty cool. But yes, SSD speed has very little to do with copy speed in this case.
I wonder if this could be used to infer information that users may not intend. For example, perhaps copying a file and fraudulently altering something in it at a specific time could be used as evidence in a trial.