This isn’t about the PMP A330-300 aircraft which is incompatible when having FBW installed. It’s about the Headwind A330-900neo aircraft. Which is a standalone aircraft on its own. It has utilized the 0.6.x version of the FBW systems. But it does not require the FBW aircraft to be installed, it’s operating independently regardless of which FBW version you have installed (or not installed).
As for OP’s problem. I’m not sure yet. I’ve been using the MSFS fuel and payload slider to fill in fuel, but I don’t think there’s a problem. (Or maybe I never realised it since I just fly just fine with the loaded fuel).