Did you enable the service mentioned in the guide?
sudo systemctl enable --now grub-btrfsd
Yes, it is amazing! It makes subvolume, snapshot, and Btrfs filesystem maintenance practically trivial, even some advanced functions. It really is one of the best apps, so well done and useful.
You may be conflating Btrfs Assistant and Snapper. In my opinion Snapper is better than Timeshift because it is more featureful and can be more precisely controlled, but it is just my opinion. Some folks maintain that Timeshift is easier to understand.
Btrfs Assistant can be used to manage snapshots from either Snapper or Timeshift.