Like all video games, they had to make change before releasing the final version. RCT2 is no exception.
Side friction coaster were going to feature curved drop, and a steep drop. Side friction coaster was going to derail off the track if it took a turn too fast.
Heartline Coasters were going to have a vertical lift, loops, and a dive loop, as well taking corners. Feel free to add your own if you discover somethings in OpenRCT2 that didn't make it to the final version of RCT2, and its' expansions.