I had something to add the last time this came up but I can't remember which book it was in.
I thought it was in The DH Story by C. Martin Sharp but I haven't been able to find it without re-reading the entire book.
Since I can't find the actual quote I can't add the exact job descriptions or positions but from what I recall, a production manager went to the design dept. saying they were having trouble achieving the specified clamping pressure when bonding around the windows/openings.
That was the only reason for adding the rivets.
Joy ride blamed conservative management last time too, I'd like to know on what he bases that accusation. Over-ruling a Chief Designer on matters of design sounds more than unlikely to me.
Obviously I'm not an aircraft designer and hindsight would prove me wrong but 3 in corner radius sounds generous to me, certainly a long way from the widely reported "square".