That is what the video implies - selective thinking is one of many tricks human mind employs to get a given task done. No way it is trying to say that you must also have noticed gorilla. Eg, if you are intraday trader then you have to be selective of intraday setups, that means the gorilla positional setups will have to be automatically in blind so that you can focus on your intraday trading. Vice versa is true for positional trader.