I also had a similar issue with the grub menu list, and here's how I fixed it.
/etc/default/grub.d/50_kubuntu.cfg passes on "Kubuntu" as the name of the distribution to
update-grub. If you want to change it back to Ubuntu, the fix is as simple as:
sudo rm /etc/default/grub.d/50_kubuntu.cfg
If you want to change it to something else, just edit
/etc/default/grub and change the
GRUB_DISTRIBUTOR line to whatever you want. Example, change:
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_DISTRIBUTOR="My very own Ubuntu install"