It seems that the Fall Update brought with it more than we realized. A befuddled Knuckles Dawson IMed us the other day, noting that backwards compatible Xbox games are now showing up on Xbox 360 Gamercards. We checked our own console, and sure enough, a recently played Xbox game (Ninja Gaiden) was displayed. The games do not appear on Xbox.com Gamercards, only on the 360 itself (under the Games Played tab in the Games blade). Also, only games you've played since the Fall Update will show up. In other words, our jaunt with the Halo 2 maps released earlier this year isn't recorded. The most curious bit of all is that the games are listed with the notice "0 of 0 Achievements."
There are a few possibilities here. The most likely is that Microsoft thought it was a good idea for all games to show up on the list, especially given the arrival of the Xbox Originals service. Much less likely is that Microsoft is looking for some way to implement achievements in old Xbox games, which Major Nelson has stated isn't the case. No, we imagine it's there simply for convenience (or inconvenience, depending on whom you ask).