Games go through changes between pitch and release. This isn't new information, it's just the way things are. Silent Hill: Shattered Memories is one of the games that went through a substantial amount of changes. It was Silent Hill: Cold Heart and a drastically different game to begin with.
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The site Silent Hill Memories managed to get a hold of the original 14 page pitch for the game that outlines what the original concept was for the game would eventually become Shattered Memories.
This book is a neat look into what goes into pitching a game. It's not all just throwing cool effects at a board and hoping for the best.
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The pitch details not only what the story would have been but also what players may encounter in the way of gameplay and puzzles
The biggest difference is perhaps that the game wasn't supposed to be a sort of reboot of the series. Instead, Cold Heart was its own standalone addition to the series with a new storyline. This is obviously not how things went.
Also, the gameplay was very different. Although they both featured terror and horror, Cold Heart was going to be a more traditional Silent Hill game when it came to combat and monsters.
You can check out the full 14-page pitch and compare how the two games differed. Silent Hill: Shattered Memories came out in 2009 for both the Wii and PlayStation 2. You can see a trailer for the game that was below.