Quotecan be inherent to some LCD panels where the display refreshes slightly slower on one side of the display to the other
ALL displays. They ALL refresh the screen line-by-line AFAIK. The jelly screen effect is visible on my Surface Pro when in portrait orientation, and nobody complained about it. I think it's just the nature of the Ipad Mini: people use it in different orientation much more, so it's more noticeable. It's also not « one half of the screen » that is slower to refresh, it's each pixels on the horizontal line, because you have to refresh the entire vertical row of pixels before switching to the next. It's progressively slower on each line.
If you know of a model of LCD screen that changes the refresh orientation of the screen when turning the device around, I would be very interested to know, that would be pretty interesting to teardown. But I don't think it exists, contrary to what this article is telling.