Strange resolutions? How do you set up 1280 x 720 resolution in raw?

[MilesThatch]

Pardon me for what may be a simple question. I don't understand why there are no simple 1280 x 720 options in the raw resolution setting. (EOS M) Is it dependent on the lens you are using? I can shoot native 1280 x 720 but when shooting raw, the video files get stretched in some disproportionate manor. Not sure if it's the way raw recording acts or if I'm just not setting up the recording right.