The sentencing will take previous convictions into account, though, and the arrests were made on the basis of video evidence. I expect that anyone waving their arms would be unlikely to be prosecuted. Having said that, in the 2011 riots people were jailed for 'looting' water - I remember one young man got 6 months for that, and he wasn't rioting - it was an 'opportunistic' theft that he committed on his way back from his girlfriend's house when he was thirsty. He was a student, and I imagine the sentence will have messed his life up significantly.
Still, the message is loud and clear - if you are in an area where there is violent disorder, do as the police tell you and don't break the law. Also you can't rely on so-called 'two tier policing' to get you off the hook if you're middle class, which is probably fair enough.