They manufacture and sell both types and have no intention of phasing out the "older" model with deeper roof.
The newer models have a reduced footprint and are popular with keepers who practise migratory beekeeping as they can get more hives on their truck.wagon etc Also the "newer" crown boards have a singe vent hole plus a recess designed to hold a 2.5 litre Ashforth type feeder that they sell. I buy newer crown-boards + feeders but buy the deeper roofs so no compatibility issues with nay of my hives....I still have a few wooden Nationals that get brought out as required.
If I get some time I'll pictures and show you the differences.