Here is the original post I made about this in case you missed it:
https://forums.unraid.net/topic/61985-file-browser-in-webui/page/2/?tab=comments#comment-723474
What I am suggesting there for "surprise" #1 is not a warning, but instead that any operation that would cause the "User Share Copy Bug" not be allowed at all. The problem is at the Linux level of things, but at a higher level it isn't that hard to detect when a move or copy would cause this problem.
And for "surprise" #2, the suggested workaround is explained there in that post.
So, if a file explorer were implemented, it would need to do some things other than just passing it to Linux to carry out the move or copy.