[android] How can one pull the (private) data of one's own Android app?

Does that mean that one could chmod the directory from world:--x to world:r-x long enough to be able to fetch the files?

Yes, exactly. Weirdly enough, you also need the file to have the x bit set. (at least on Android 2.3)

chmod 755 all the way down worked to copy a file (but you should revert permissions afterwards, if you plan to continue using the device).