I actually never understood the parallel neutral violation in cases like this. Where is the hazard? I think in an emergency situation where connections may be shaky, I would rather have a redundant neutral/ground path than have 2 separate ones. You might argue that the generator frame could be at a slightly higher potential but we did that for decades with 3 wire feeders and 2d buildings and dryer frames. If you are worried set the way back machine to 1995 and drive a rod.
