It arrived and works just fine. I did have to get the latest version of WinUAE though... Well Hybris marathon tonight! 
Does this mean that this joystick adapter will only work with emulators that specifically support it?
As I said, I hacked a DB9 port onto a standard USB controller and it will work with any PC game or emulator that supports a regular USB gamepad.
The adapter you bought is smaller, but if it only is supported by certain emulators (or certain versions of emulators) then not sure it's an advantage...