bjs, what can I say? It's not drugs, so I guess I'm an eccentric geek
It gets stranger. I tried the directory bind, and it didn't see any source directory contents. I'd done the first test (1) with ES File Explorer. So I tried a second test (2) with Root Explorer and got different results. Then I tried another test (3) with ES File Explorer again. The results with numbers worked. The ones with Xs didn't. The ? means I didn't try that path during that test. Directory Bind will tell the truth, but it didn't work with the one path that worked with both file explorers.
1 2 3 /mnt/shell/emulated/0/usbstorage/sda1/iBird_Pro
X 2 X /mnt/sdcard/usbstorage/sda1/iBird_Pro
X X X /data/media/0/usbstorage/sda1/iBird_Pro
X 2 X /sdcard/usbstorage/sda1/iBird_Pro
X 2 3 /storage/sdcard0/usbstorage/sda1/iBird_Pro
X X 3 /storage/emulated/0/usbstorage/sda1/iBird_Pro
? 2 3 /storage/emulated/legacy/usbstorage/sda1/iBird_Pro
Edit: None of the paths worked with Directory Bind! I'm not sure what to do next.