I also have this issue, but altogether with the following one: Sd-umount: Failed to unmount /oldroot during each boot/shutdown.
I followed the proposed solution here:
… and it helped me to resolve that particular issue, but the original issue in this thread still remains, even I followed your steps precisely. I tried all of the following combinations in my /etc/mkinitcpio.conf and none of them helped:
# 1. try:
MODULE=()
HOOKS=(base udev autodetect modconf block filesystems resume keyboard shutdown)
# 2. try:
MODULE=(nvidia nvidia_modeset nvidia_uvm nvidia_drm)
HOOKS=(base udev autodetect modconf block filesystems resume keyboard shutdown)
# 3. try:
MODULE=(nvidia nvidia_modeset nvidia_uvm nvidia_drm)
HOOKS=(base udev autodetect modconf block filesystems resume keyboard)
After each change of configs from above I executed these:
sudo mkinitcpio -P
sudo grub-mkconfig -o /boot/grub/grub.cfg
sudo systemctl restart systemd-coredump.socket
sudo systemctl reset-failed
Technical details:
My main NVMe Disk model: Samsung SSD 970 EVO 500GB
$ sudo fdisk -l
# [...]
# ends with:
Partition 1 does not start on physical sector boundary.
NVIDIA-SMI 460.80 Driver Version: 460.80 CUDA Version: 11.2
Any ideas? 
EDIT: Seems like an old bug. It has been reported upstream: