The difference between the old and the new Geeza design is basically following the centuries old principles of making type better readable on a smaller size. First, the stroke has to be made thicker and second, the height of the ascenders and descenders have to be reduced in relation to the x-height. This intervention changes the stroke/space balance. Within the 'bounding box', there will be more letter so to speak. As said, nothing new, in 1931 Stanley Morison made this 'invention' with his design of the Times typeface, which started the era of modern type design.