btrfs restore -i -v /dev/sda /srv/dev-disk-by-label-NewDrive2 | tee /restorelog.txt
Came immediately back with 'Reached the end of the tree searching the directory'
I'm actually not surprised, given that the restore command didn't really do anything. I again wonder if I shouldn't try it with the second ddrescue drive that I made to look at, but never did anything with.