Comment # 6 on bug 1195291 from Martin Wilck

(In reply to Michal Suchanek from comment #5)
> You don't need to reinstall bootloader when the set of kernels and ramdisks
> before and after adding/removing the package is the same.

Don't we do this already ? We trigger bootloader installation only if the base
package is added or removed, not for -extra or -optional.

@Ulrich, I'd advise you to set GRUB_DISABLE_OS_PROBER="true". We disable it by
default on SLE for a reason. If there are other installations on the same
system, you're usually better off with a custom.cfg that looks like

menuentry 'partition 3' {
    set root=(hd0,3)
    configfile /boot/grub/grub.cfg
}

etc.