Meaning of statement that 'getcwd functions work correctly' in FreeBSD man page for mount_nullfs?

In FreeBSD, [man mount_nullfs](https://www.freebsd.org/cgi/man.cgi?query=mount_nullfs&apropos=0&sektion=0&manpath=FreeBSD+11.1-RELEASE+and+Ports&arch=default&format=html) states that: > The primary differences between a virtual copy of the file system and a symbolic link are that **the getcwd(3) functions work correctly** in the virtual copy, and that other file systems may be mounted on the virtual copy without affecting the original. A different device number for the virtual copy is returned by stat(2) , but in other respects it is indistinguishable from the original. What is the full meaning/implication of this paragraph?