Plate rivet joints are a different design case. And expanding rivets were/are used for the reason mentioned.
Steel/steel joints are mostly designed both for friction and bolt shear. Friction caries the normal loads but if something goes wrong in the chain of events the bolts still have the capacity.
In the pickle fork case at least the fork is Al, don't know about the center wing box. I have never designed a steel/Al joint but might be that the three fold difference in elastic moduli could cause some trouble. Al's low bearing strength would be a problem with that large steel bolts. I still think friction is included.