Why don't Grub 2 options work in Ubuntu 17.10?

Question

GRUB

I want to remove the OS selection menu and leave the first item to boot - Ubuntu. The default timer is 10 seconds.
/etc/default/grub settings:

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'

GRUB_DEFAULT=saved
GRUB_SAVEDEFAULT=true
GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=0
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""

# Uncomment to enable BadRAM filtering, modify to suit your needs
# This works with Linux (no patch required) and with any kernel that obtains
# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"

# Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL=console

# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480

# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true

# Uncomment to disable generation of recovery mode menu entries
#GRUB_DISABLE_RECOVERY="true"

# Uncomment to get a beep at grub start
#GRUB_INIT_TUNE="480 440 1"

$ sudo update-grub
Генерируется файл настройки grub …
Найден образ linux: /boot/vmlinuz-4.13.0-32-generic
Найден образ initrd: /boot/initrd.img-4.13.0-32-generic
Найден образ linux: /boot/vmlinuz-4.13.0-31-generic
Найден образ initrd: /boot/initrd.img-4.13.0-31-generic
Найден образ linux: /boot/vmlinuz-4.13.0-25-generic
Найден образ initrd: /boot/initrd.img-4.13.0-25-generic
Найден образ linux: /boot/vmlinuz-4.13.0-21-generic
Найден образ initrd: /boot/initrd.img-4.13.0-21-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
Найден Windows 10 на /dev/sda1
завершено

No matter what I change, nothing changes. sudo update-grub did. What is the reason?

Answer 1

As far as I remember,
GRUB_HIDDEN_TIMEOUT=0
GRUB_TIMEOUT=0
cannot be written at the same time.