(1) It is more logical to determine the grub installation options by detecting EFI partition
(2) If it is not possible, you should at least have proper instruction that says, "Fxxk off dude. If you don't wipe clean your harddisk (probably with the Windows and all other data on it), don't install Ubuntu."
What I'm saying is,
(1) It is more logical to determine the grub installation options by detecting EFI partition
(2) If it is not possible, you should at least have proper instruction that says, "Fxxk off dude. If you don't wipe clean your harddisk (probably with the Windows and all other data on it), don't install Ubuntu."