Yeah that is a silly loophole. If it's dangerous enough to ban ( and it is) how can social media be a justifiable exception. Unless they implicitly trust the people that run social media companies for some reason?
My guess is that they lack the jurisdiction to regulate how (for example) Facebook processes images on their platform. Rather, the ordinance only applies to entities while they are within the city. So without the social media exception, it would likely be illegal for any individual within city limits to take a picture with the intent to upload it to Facebook. That would make for some interesting fallout to say the least.