Yeah, it's another one of the many things that the Windows kernel gets right but *nix programmers never care to give it credit for. `FILE_LINK_INFORMATION` in Windows has a `ReplaceIfExists` flag just for this purpose.
The only reason I suspect things do unlink-then-rename is that (evidently) rename() doesn't promise anything about what happens to the "src" item if rename() fails, just that something will still be in "dest".[1]
But I don't know why the commands do something different, and don't want to try reading the source of either GNU or BSD mv to find out why.
[1] - http://pubs.opengroup.org/onlinepubs/009695399/functions/ren...
If it doesn't exist in practice or does something different in a thousand edge cases, it's rightfully dismissed as nonexistant.
The new WSL does have symbolic links, but these are only available to Linux programs.
An application should not change the default security policy.
When someone uses the term "symbolic link" to mean something different than someone else using the term "symbolic link", we can assume they:
(a) do not understand what UNIX is calling a symbolic link, either because they have never heard the term, did not research it properly, or have some kind of learning disability
(b) are attempting to intentionally confuse users
We do not assume that "symbolic link ``features''" now means something else: We need justification to do that, and we don't have it:
A "link" is what POSIX calls a directory entry (§3.130), and a "symbolic link" is simply a directory entry (link) without a file associated with it.
When we are thinking about this clearly we can see what Microsoft did wrong, but we're under no obligation to support them in their definition because clearly their definition is less useful than the POSIX one.
> Some Linux distro could implement the same policy,
Users would revolt; they did revolt.
SELinux was popularized by a number of Linux distributions, and included a configuration that did exactly this, however people just turned it off because breaking applications pisses people off.
> but symlinks would still be symlinks.
No.
Just because they use the same words does not make them the same thing. You can use α-conversion to fix this without anyone else's help, and call Microsoft's "symbolic link" foo and UNIX's symbolic link bar, then you can find the sentence "foo would still be bar" the nonsense that it is.
All the other still apply, and the GP forgot to tell you to check your HD model's documentation.