[Walt Fricke]

This hardware can take quite a bit more torque than the factory spec.

But as Craig points out, if the threads on nut, bolt, or both are rusty or otherwise have a higher friction coefficient, more of the torque will go into turning the nut, and less into stretching the bolt. And bolt stretch is what draws the ends together and expands the shaft ends to lock the shafts in place.

The issue isn't that the nut end isn't holding by itself toward the end of the tightening. It is whether or not the shaft ends have been adequately expanded against the bores, so the shafts don't walk while the engine is running. You might put force on them to see if you can push them. I'd not go overboard with a miniature porta-power or sledge hammer.