An svn copy is just a link. It has always been a "free" operation (and yes, the analogy would be to a symlink). I'm not aware of any version of svn that behave

An svn copy is just a link. It has always been a "free" operation (and yes, the analogy would be to a symlink). I'm not aware of any version of svn that behaved the way you described and I've used it for a couple of decades. I can perhaps imagine a large repo plus a broken svn client requiring checking out unneeded portions of trees to do a copy, but no client I've used works like that. Hm. Another theory. Perhaps someone who knew nothing about svn and was using TortoiseSVN's Windows file manager integration was doing a Windows file manager copy, then checking that in as a "branch" with the only link being the commit message instead of using svn's copy which is free and properly links content. That would indeed be an expensive operation, and the wrong thing to do.