I know in the CF6-6 and -50 engines LPT Coupling nut was at the end of the LPT ,,,,the hot end of the engine ,,,stays nice and dry , The Genx is at the front of the engine ,its always more cold and moist (visible during ground runs ). This means it cycles cold to ambient numerous times and creates moisture each time. The Genx flight testing was done at Victorville in the Mojave Desert,where its nice and dry, the failure occurred in the South where its wet and humid. If the LPT coupling nut was over torqued, or the threads damaged in handling or manufacturing, and the Anti-cease is now hygroscopic, I suppose this could create accelerated corrosion, but I think it is more likely since the short time on these engines that they were damaged upon assembly. Worst case would be a design flaw of having chosen to put the coupling nut in front ..........I don't know if the GE-90 is designed in this configuration? But I would assume this allows replacing the propulsor easier?