If the nut is tightened correctly (leaving 1 1/2 threads visible) the scissor shackle fits perfectly. If you overtighten the nut the scissor shackle gets compressed and that is what some of us feel is the issue here.
Yes, a shouldered bolt would potentially prevent this, but it would be up to the boffins at M-B to analise and sanction that kind of change. They may well have had their reasons for using this assembly. To be honest, the basic design of that assembly had not altered much over many years and I understand Typhoon and Lightning II seats are significantly different in this area.
Just to inform, this operation would not be carried out in a Seat Bay, but would have been carried out by 1st line armourers during the act of fitting the parachute headbox.
For what its worth, I would still rather have a M-B seat than any other!