Because you don't pre-clear, you leave from the International section of the airport. In Toronto, the nonstop to Hawaii leaves from Terminal 1 instead of Terminal 2. The reason is that most people are going on to Australia and New Zealand so they sit in the big transit lounge at HNL. If you arrive into HNL very late you may have to get on a shuttle bus under guard to get to the clearance area. On the return, the flight may leave from the transit lounge area, which means that you leave the US area within the airport.