Sorry, I made a mistake and didn't mean 4K. There are other threads in here with users discussing which Vimeo and Youtube videos they are using to show off their Retina display. So, if those websites only allow up to 720p to the iPad, are those other users just mistaken and not realising it doesn't show what the Retina display can do at all?
In other words, the only way to show off the retina display is to import a video file onto the iPad that uses the increased resolution. There are videos on Vimeo and Youtube claiming to be much higher than 720p or 1080p (4K the highest I saw on Vimeo). Is it correct then that those higher resolution videos won't play on the iPad, and that they will be scaled down to 720p? :/