Moving and copying multiple targets

So, I've finally spent a few minutes to investigate what it would take
to move and copy multiple files in one command, akin to the way that
normal (non-svn) move and copy commands typically work. In a previous
patch[1], I tried implementing this completely in the client
application. Since then, I've done a little bit of investigation into
existing subversion commands which take multiple arguments, and I've
discovered a couple things for which I need a little clarification.
[1] http://svn.haxx.se/dev/archive-2005-11/0393.shtml

In the client application, the add command does *not* push multiple
targets at once down to the client library. It simply loops over each
file to be added and makes a separate call to the client library. It
was pointed out that for move, this is *not* preferred; what about add?

To help me understand better, why would it be better for only a single
call to the client library from the client application for a move or
copy command, instead of looping like the add command? In my
understanding, we don't have to have atomicity because we aren't doing
something like a commit, which does send all of its arguments to the
client library at once. I don't have a position on which is better or
not, just wondering why.

Thanks for the help.

-Hyrum