The splined interfaces would be making direct contact way before there would be any significant shear stress going through the bolts. To get to that much force on the bolts, that entire splined interface would have to fail and shear off, and that's just not happening at human torques. Besides, no reason for 3 bolts on xcadey to be weaker than 3 bolts on standard sram. It's supposed to be the exact same design, just adding another two bolts, presumably to get around the patent.