Is there some reason why capital & lowercase versions of some of the letters are so different? If it's meant to resemble Arabic that might suggest they are diff

Is there some reason why capital & lowercase versions of some of the letters are so different? If it's meant to resemble Arabic that might suggest they are different sounds,not just a lowercase or capital versions. I don't see why different characters makes sense at all. This seems to be a featural alphabet, but not being a linguist the "front/mid/back" stuff is nonsense to me too.