If Split Keyboard is enabled (Settings | General | Keyboards), when the keyboard appears, it rises too high, obstructing more screen area that it should. Normal behavior is to rise until its bottom edge only just appears at the bottom of the screen but in this case it rises the equivalent of ~2 rows of keys too far. This happens with system text-boxes as well as application ones and in either orientation, but only if Split Keyboard is enabled. Reported in Apple Feedback.