[Someone]

"detect device type and capabilities and load resources accordingly on app first run."

That is not sufficient. You also would have to detect the case where a backup is restored to a device with a different resolution (could even be a lower resolution)

"you will have to foot the bill for your free graphics-intensive app getting three million downloads."

Not necessarily. The App Store could have provisions for doing these kinds of downloads. Because of the backup issue, I even think it would have to have support there, given that Apple would want to prevent the cases "sorry, cheapGames.com's server is awfully slow" or "sorry, junkSite.com's server has disappeared; we cannot get you the graphics for that game you bought anymore" (site names made up; if they exist in real life, the name match is coincidental)