Interesting, thanks for writing this up (as well as your hard work testing of course!) It should be extremely helpful for people wanting to backup or transfer their save files on android.
Yes, I also tried it with a simple tar command and it also works, I suppose it shouldn't be too hard to add basic save import/export support to your apps if you ever decide to, however that would have the side effect of allowing people to exchange save files, that may be undesirable if you release paid features.
If you decide to add this you'll probably need to use a tar library (I say tar because it backs up file permissions by default, though you may not have this issue since your app will be doing the copying).
Anyway if you want me to give you the steps to do this just say so.