https://bugs.winehq.org/show_bug.cgi?id=45935
--- Comment #13 from Zebediah Figura z.figura12@gmail.com --- (In reply to Joshua from comment #12)
Because copy+delete runs the significant risk of picking up half a file. We've seen this fail already when somebody insisted on not doing the rename dance. Locking doesn't help when one of the risks is loss of power.
I'm failing to understand what you mean by "picking up half a file". If someone's writing to the file that's being copied to while it's being copied, well, I guess it's their own fault for doing so, but I don't know how that would differ in the case of an atomic rename.