I figured it out. I thought it was dropping down next to the platform that has the down arrow, like everyone else thinks it's supposed to work. The actual solution is to stand on the platform with the down arrow, then walk down that same platform, vertically. Not drop-down, not jump, just walk down the path, like a bridge. No need to jump or do something crazy. It is a bit ambiguous, but it works at least.
While I'm here, does anyone have a full list of the game's soundtrack? I know I can listen to it in the OpenBOR pak launcher, but I wonder where most tracks come from. Obviously some are from the Sonic franchise, but I also heard some Streets of Rage and Pac-Man Championship Edition DX. I'm really curious now.