Sega Vintage Collection titles disappearing on the ESRB

One of the juicy tidbits of information from the ESRB pointed to the rumored Sega Vintage Collection where classic Genesis games would be playable on the Xbox 360. Sonic the Hedgehog, Ecco the Dolphin and Sonic the Hedgehog 2 were rated by the ESRB as Xbox 360 games. However, the ESRB updated their database and listings for these games are gone. While the ESRB is a good source for information on unreleased titles, a rating does not guarantee a game is going to come out.

Did Sega pull the plug on the vintage collection? Did the ESRB make a mistake? Or did Sega ask the ESRB to remove the listings to keep the service under wraps?