The BUGs are still large 20kva gens, frequency wild machines that are directly driven by the engine gearbox that can provide power in tbe event of a main gen failure. The FADEC alternators are tiny units designed only to provided power to the FADEC EECs, very easy to drive by a small wind turbine, also designed to give a useable output at low rpm for windmilling air starts etc. Yes the output would have to be rectified but that only requires a few diodes.