I have openSUSE 13.2 installed on on my first Crucial MX300 535GB SSD drive and
Tumbleweed and 42.2 beta 1 on my 4th drive.

When I run the Yast2 boot loader or grub2-mkconfig -o /boot/grub2/grub.cfg, the
first grub2 menu entry shows 'Found unknown Linux distribution on /dev/sdd1'.

I originally thought that it was due to me using btrfs so I reinstalled using
ext4 fs for my / (root) partition. The same menu entry appears.

The advanced submenu & menu entry shows:
submenu 'Advanced options for unknown Linux distribution (on /dev/sdd1)'
menuentry 'openSUSE Tumbleweed  (on /dev/sdd1)'

Note that openSUSE Tumbleweed appears in the menu entry below the submenu.
Refer to my grub.cfg file that I've uploaded.

I believe this is do to changes made to the location of the os-release file.
The original os-release file was only located in /etc/os-release. 

Now it's located in /usr/lib/os-release and a link has been created pointing to
/etc/os-release.

ln -s /usr/lib/os-release /etc/os-release

Is it possible that the code in os-prober cannot find nor read the link in
/etc/os-release?