No, the police don't have to arrest you to question you for hours. They have a time limit where they have to let you go or charge you, but a) it varies by state and b) it ranges from 48 to 72 hours.
You're mixing up a stop with an arrest. If the police have reasonable suspicion, they can detain you only as long as necessary to investigate that suspicion. Usually that means minutes, not hours. If they have probable cause, they can actually arrest you, search all your belongings, search your person, and hold you for days before charging you or letting you go. The story claims he was only detained, not arrested.
Actually, I'm not. Police can detain you for questioning for 48-72 hours, depending on jurisdiction. After that time, they must either arrest you or set you free. Things are much worse for people classified as "material witnesses". One such person was held in prison for 16 days. https://en.wikipedia.org/wiki/Material_witness
