I think you are misunderstanding, using Supercruise Assist isn't cheating. When you target a station and fly the entire way to it using Supercruise Assist, it flies you at 75% throttle all the way to the station and then drops you out automatically.
The exploit involves not activating it until the last moment. So rather than flying at 75% for the whole duration, or flying at 100% until the destination timer reaches 0:06 seconds and then dropping to 75% and gradually slowing down. You're flying at 100% speed until the final moments and don't have to slow down at all.
Using SC Assist the whole journey will take the longest.
Using 100% then 75% throttle, is faster.
Using the exploit is far, far, faster.