If you use a certain device for your Nintendo DS that can enable you to Walk through objects, head to Mt. Coronet and explore the Snowy Mountain part thoroughly.
You'll notice some parts are cut out.
I'm guessing they were going to make Mt. Coronet bigger in Platinum because of the new plot.
Examples:
There is a hidden place where you can use Rock Climb. Use it there, and you'll end up on a black voidless background.
A hidden hilltop with Rocks that you can smash. There is no legit way to get here.
You'll notice some parts are cut out.
I'm guessing they were going to make Mt. Coronet bigger in Platinum because of the new plot.
Examples:
There is a hidden place where you can use Rock Climb. Use it there, and you'll end up on a black voidless background.
A hidden hilltop with Rocks that you can smash. There is no legit way to get here.
