I was under the impression that they received a prompt offering to restore the snapshot they were booted into. Btrfs Assistant doesn’t do that.
the client app of btrfs will list any timeshift or snapper snapshots directly, revealing their relative path.
The snapshots can be restored from that list accordingly.
You are correct, I booted into a snapshot and a prompt appeared asking if I wanted to restore to the snapshot. I’ll try to see if I can get it to appear when I boot into a snapshot and if so, try to figure out what it is.
Oh wow, someone is going to explain to @dalto how Btrfs Assistant works. 
If you installed snapper-tools, that is likely what is providing the notification. It looks like this:
I found this funny also, I am newer but I see his name on a lot of BTRFS issues.
That was it. @dalto - I didn’t get to check but that was the box, so I would say snapper-tools which was on the walkthrough that I followed.
So in that case, it was snapper tools that did the restore, not Btrfs Assistant