Question on machine design

[f350ca]

Was just on the phone with a friend who's replacing the crown and pinion in his old Case backhoe. The crown is riveted rather than bolted to the carrier. He's an automotive, as well as heavy duty mechanic, along with mill wright. Neither of us can remember seeing a differential that didn't bolt the crown in, is this common in tractors and if so why. Only reason we could come up with was, on a loader there is a lot of forward and reverse, so maybe the crown could walk on the bolt clearance. Properly riveted there should be an interference fit in the holes. Any thoughts?
Greg