I suspect that the attempt was to minimize the water jacket complexity in the block and head castings and trade that off for a more complicated water pump casting. It isn't the most fun water pump in the world to change out, but it also is far from being the worst!

Modern flat ribbed belts with tensioners are a huge advance over the old multiple V-belt way of doing things. One must remember that the basic red block design goes back to the 1950s! The overhead cam versions were a major retrofit onto a pushrod design with a vestigal camshaft still in the block like an appendix :).

John