I got something.
The saves are in, they are visible, but can't be loaded. That is progress if nothing else.
Did it in an emulator without root. If you want to test it yourself, untar the backup.tar. In there you'll find an 'r' directory, upload it's contents as seen on screenshot (tar -> push -> cat-pipe-(run-as dd) -> run-as untar) and from the 'sp' directory upload that one file to 'shared_prefs', also in the run-as jail.
I'll see what I can do about the whole not loading thing.
Or I guess you could upload the backup.tar, untar it into some temporary dir and cp the files from the temp dir to their correct place. That should work too.