svn update consumes a lot of data on directory rename

I did a "svn update" (svn+ssh scheme) over a mobile connection,
and this consumed several dozens of MB, while there were actually
very little changes. There was a rename of a directory with large
files, and I suspect that this was the cause. I thought that the
system of "cheap copy" would avoid that. So, why this issue with
data transfer?

-- 
Vincent Lefèvre <[email protected]> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)