When you go to the Halo 3 game detail page on xbox.com you see the image on the left. You could interpret that a number of ways, but without any preceding text, I would expect that the same runs in 1080p, which is 1920x1080, not scaled to it. That makes Halo 3 1,335,040 pixels shy of a true 1080p HDTV image. That is a huge number. Scaling can only get you so far before it's noticeable, you can't just invent millions of pixels without anyone noticing. Scaling down, no problem there, my equipment isn't up to snuff, but scaling up without consumer knowing about it, I have a huge problem with that. What about when you buy an Xbox 360, is anything said on the marketing that would lead someone to believe High Definition was a feature?
On the Xbox 360 Pro info page, you see the text in the images to the left in different spots on the page, but that's it. Microsoft's language here never explicitly says something like Experience gaming in True HD, but I do think the expectation is created between what you see on the Halo 3 site, and the retail box, and what you see on the Xbox 360 site that you are going to be gaming in true high-definition, the image you see will be native HD, not scaled to that output resolution.
I don't think it's a stretch all, I know that is what I expected with the 360 and absolutely for Halo 3. Apparently it's not just Halo 3 that has this problem, but a decent number of other games also render at less than HD resolutions.