/etc/fstab: meaning of "nofail" if "noauto" is already specified

Just for the record:

For an external USB disk which is usually not connected at startup, I have an fstab entry

/dev/disk/by-label/data /data   xfs noauto,user,noatime 0   0

When booting there is no error as noautokeeps the system from trying to mount. When I try to mount manually without the drive connected, I immediately get the error

~$ mount /data
mount: special device /dev/disk/by-label/data does not exist
~$ 

If I change the line in fstab to

/dev/disk/by-label/data /data   xfs noauto,nofail,user,noatime  0   0

there is no error reported, even when the drive is not available:

~$ mount /data
~$ 

System: Ubuntu 16.04 with systemd.