Earlier quoted context omitted.
>* overwriting a folder deletes existing contents, rather than merging them Wait. If there truly is not a setting for this then it makes finder unusable as a file explorer and arguably the entire OS. Recursive merge is one of the most fundamental things a personal computer does.
that's the pretty standard behavior on unix. Unless the window manager goes out of its way to override it, mv'ing a folder to a place where one already exists will replace the old folder with the new one. You can go out of your way to do it manually with rsync and similar tools, of course, but by default you're moving directory pointers around, not merging trees.
Not even slightly:
$ mkdir 1 2
$ touch 1/foo 1/bar 2/baz 2/quux
$ mv -T 2 1
mv: overwrite '1'? y
mv: cannot move '2' to '1': Directory not empty
$ mv --force -T 2 1
mv: cannot move '2' to '1': Directory not empty