A crack in Hamming’s own passage.
He offers the move from screws and bolts to welding as successful redesign for mechanization (Screws and bolts became rivets and welding). He also insists that Field maintenance must be part of the original design, and screws and bolts are the maintainable join: reversible, serviceable, replaceable in the field. Welds are not.
So his illustration of good redesign is a case where production economics won and serviceability lost. He does not remark on it.
That makes the example more useful than he intended: Equivalent product hides a choice of metric