If the Share Branch is on a shared folder, it is implied recursive. If a folder branch is applied to a Secondary Share on a folder, the operation is a Copy Branch rather than a Share Branch, meaning you can only Share Branch from a Primary Share.
For example: If a share was done on $/foo and a branch is applied to $/foo/subfolder, then the Copy Branch command is invoked on $/foo/subfolder, and you would choose another location to copy the folder to. $/foo/subfolder would remain shared after such a branch. Breaking the share must be done at $/foo. This applies to any files as well. For example, $/foo/abc.txt would invoke a Copy Branch on abc.txt, not a Share Branch.