Yes, if you check the “mount at system startup” checkbox, it’ll update fstab for you. My only problem was when deleting partitions on gnome-disk-utility, it doesn’t automatically delete the fstab entries it previously created. You’ll need to manually clean it up yourself. This might cause mount problem if you delete and recreate the partition with the same mount settings because there are now two fstab entry, where the first entry references partition that no longer exist.