This means that the touch sensitivity for the y axis is higher than the x axis, maybe because the game doesn't accomodate the sensitivity ratio for devices that have an aspect ratio higher than 16:9. Which means that if you have a device that has a wider aspect ratio than 16:9 if you were to move your crosshair along in a small and almost perfect circle your thumb would be moving along but in a wide oval instead of a small, semi-perfect circle. With my phone that has a 20:9 aspect ratio It's incredibly noticable and disorienting for me, especially because I only use split controls. I've even had this problem on an older device that had an aspect ratio higher than 16:9.