The curvature of that tab section on the pouch is due to the leather being riveted on slightly off rather than flat against the pouch. Given that up until these pictures, most references (which were blurry screencaps at best) would make it appear to be a curved cut piece so it comes as no surprise that the replicas out there would cut that section with a curvature. Also note that they used different weights of leather to create the belt and some sections are thicker or thinner than others.
I have even better materials for this costume and belt and I'll be remaking it soon. It will blow the previous version out of the water by comparison. In fact I have some really incredible fabrics I've sourced for a number of SW costumes and I can't wait to show you all because it will put earlier iterations I've done to shame.
Is the raw silk for Obi´s ANH costume identical to what Yoda´s robe was made from? Interested to know, where´d you find it!?