Itís a matter of selection in my opinion.
Hence why itís writen in the standard ,most breeders would cull it.
But I firmly believe a lot of American Asil men tend to gradually breed toward a round looking shank
When you look at the shank from the side it is still clearly flat , but a lot of breeders go toward a smooth looking front
Selection would maintain the rugged defined front or make it fade to a softer smooth scale
You see it in pullets often one sister with perfect square shanks and a sister with square yet much less defined.
That is the standard, but I've seen videos of Aseels in Pakistan and not all have a square shank. I don't think it means that there not so called pure but a fault that should be bred away from. Same with wattles standard says no wattles yet we see many Aseel with small wattles. It's all in selection and the bloodlines, example Bingham Aseel. Just saying food for thought.....