I also had a weird thought, have you ever seen those fake greatest hits stickers that some stores put over new sealed copys to make them look like there now $20 and a GH release? Possibly at one time, maybe Dark Cloud 2 and Ico, got this treatment, and that is why some sites have claimed that GH versions of those 2 exist.
I know the game Avatar: The Last Airbender, at my local best buy has this fake sticker on it. I've checked ebay for it a few times, and all i find of a GH release are the fake sticker versions. This is really the only proof i have for why Dark Cloud 2 and Ico are listed as being GH.