@Jim D. I was only going by what Ottolenghi said in the article about Ethiopian humera sesame. Given he sells Al Arz in his shops, I think it's safe to assume that fits the bill. I did look at multiple labels on Amazon and there was no mention of the source of the seeds, except for the brand that I eventually tried. It might be that all 'decent' brands use sesame seeds from that general region, irrespective of where the tahini is actually manufactured.
Edit: Just checked and my stuff was made in Turkey...