One notable design choice is the row multiplexer, from schematic perspective it is completely redundant (and only contributes additional transistors) but is the

One notable design choice is the row multiplexer, from schematic perspective it is completely redundant (and only contributes additional transistors) but is there presumably to make the ROM shape more suitable for overall chip layout (ie. trading complexity for more squarish-shape of the circuitry). Nice trick is that this mux is on the analog side which saves both on paths through mux and number of output ADCs.