Well you see when you cuff someone they aren't jailed yet. You either have to use the menu option to jail them, or press e on them twice to send them to jail. That is when you receive the 2 exp. You can instantly release them if you want.
However, there will be 1 more exp point given if you give them a full jail sentence. Plus you earn money for leaving them in jail. So it's entirely up to you. Honestly if you are in it for the exp then releasing them is the best way to get them back on the street earning crime. And instantly releasing them will make them want to come to you to get their crime removed in most cases.