It all seems so weird. It's actually easier to the the scanning on the backend compared to scanning of the user's phones. My opinion, maybe entirely wrong, is

It all seems so weird. It's actually easier to the the scanning on the backend compared to scanning of the user's phones. My opinion, maybe entirely wrong, is that it's related to how Apple operates in China. In China, Apple does not actually operate their backends, but their BE is operated by government owned business, which is "leased" by Apple. Maybe they don't want to enable scanning on BE for that reason, and over-engineered local device scanning, that really doesn't make much sense if you think about it twice?