Yes, so a client program that sees such both files with the same inode will correctly assume that both files are the same. However, the assumption is broken when using snapshots since the same inode may refer to the same file but from differing snapshots, so it's no longer the same.

They do have the same inode. Directories have inodes too, so that's not an obstacle.

We don't have hardlinks to directories because that is a terrible idea functionality wise.