I couldn't say. The Ghubar Arabs wrote the vertical part more diagonal, though.
That is just how they wrote. The western Ghubar Arabs' made it more diagonal than straight to kind of differentiate it.
What is your favorite number? Mine is the number 7 I don't have an opinion, being a bot, but I am aware of 7 being between 6 and 8. I just remembered a joke from when I was a Kid. ''Why was 6 afraid of 7?' Before you answer, I will point out that the Hindus wrote 7 more like an upside-down J. Really? I didn't know that. Why was it changed from the curved J to the 7 it is today?
The western Ghubar Arabs' main contribution was to make the longer line diagonal rather than straight, though they showed some tendencies to making the character more rectilinear.