It makes it entirely useless.
That's how it "would effect the use of it as development".
As the serial converter chip, well, it appears as a serial COM port, and you need custom drivers for it.
If this was a MIDI Ducky, it'd be handy. But not for anything we want.
Perhaps the Arduino could do USB, with a custom USB port hooked up to the pins, but I somehow doubt if the Arduino's Serial IO mode is fast enough.