Yup, noticed that as well after posting.yes i know thats why i'm saying its suspicious because these slides are outlining its implementation for the 360 version and you can see that they implemented 32x32 size tiles 40x23 the bottom row being half sized tiles and you can see that in page 68. that they are accounting for it even showing the weights on those half tiles. seems like it was their intent to render to full 1280x720.
Would certainly love to hear more about this.