[kimeccles]

I believe the Henry design accounted for several things. The washers on the exhaust manifold are curved and also very thick. When you tighten a nut onto a stud with a flat washer it is normal torque, but if tightening a curved dome shaped washer it introduces extra push back force on the nut (sort of like a lock washer). The thickness and correct cast material reduces the risk for brittle heat breakage as parts have similar thermodynamic characteristics.

Just saying there may be very good reasons. I can imagine that the engineers were doing a good job and did a lot of testing. I try to go original.