The Safari / iOS8 issue is indeed a bit more subtle:
- launching the app in fullscreen mode while the iPad is horizontal (landscape) triggers the issue, i.e. empty space at the bottom instead of top
- now launching the app while the device is vertical (portrait) gives a correct layout.
Even better, if you start the UI vertical, then you can rotate the device and it keeps correct layout. If your start the UI horizontal, will keep incorrect layout even if you rotate.
The behaviour on an iPhone is slightly different and always correct because while the device is horizontal the battery / time signal bar is never displayed anyway.