How best to disable os prober (grub2)

I don't need Grub2 to probe for other OS(s) as I am chainloading 9.10 from 8.04 (which has 'Legacy Grub').
The 3 menu entries for 8.04 in the Karmic bootloader are therefore not needed.
Question: can I just add this line to /etc/default/grub >>>
GRUB_DISABLE_OS_PROBER=true
followed by: sudo grub-mkconfig -o /boot/grub/grub.cfg (to update grub - required after making changes to /etc/default/grub)

 

It works. Now I have only the entries for Karmic.
BTW there are 2 memtest entries, one of them 'serial console' whatever that means.