"Just copy a file from folder A to folder B."
All that access control and authentication and symlink nonsense? That's a self-inflicted problem that exists only in enterprise, and shouldn't be assumed - much less created - for regular users.
Reality of software development is that the user would expect every single one of those things but they simply don't understand what they want up front.
There are three different aspects to consider in my experience; what the user says they want, what the user thinks they want and what the user actually wants.
The three can have substantial differences.
> Or you will complain if your colleague accesses your file without your permission.
This is a case of "out of scope", also security-first mindset that came from enterprise and is the inverse of how normal people expect computers to act. What if I actually don't mind or even want the colleague to access my files? I mean, that's half the reason anyone copies anything - to give it to someone else, or move it to somewhere where someone else accesses it.
What if the user actually didn't mean the files to be accessible to colleagues? Especially when the originals were, they just didn't know it? "Clueless user" problem is not something that should be solved at the level of filesystem operations. So either way, out of scope.