Very surprised that Shimano would thread the hole, then put in a cotter pin. Very educational though. My disc equipped bikes both use Avid BB-7 BB-5 so there is no bolt or pin. I don't even like juice brakes on cars due to the failure potential, but I have to admit the newer hydraulic discs feel better than the cable actuated jazz. Nicest brakes I've used are air-disc, but that's not remotely practicle for bikes🤪