ORD screening stations tend to be much quicker than LHR T5 screening stations when having a backup of passengers whose belongings are directed to be manually searched and/or ETD swabbed. LHR security screeners have seemed way more directed toward trying to punish people for not following cabin baggage screening rules and/or other expectations to make the screeners’ lives easier. Taking an electronic rice cooker as cabin baggage generally doesn’t fall afoul of US or UK airport screening rules, but things that look unusual on the bag scanner images and have cords attached to them tend to get more scrutiny than say a cabin bag full of just a bunch of socks.