This has recently been seen with alarmingly increasing frequency, probably correlating with the fact that only "leftover" plots are found: the desire to prop up a hillside plot so that it becomes level in both dimensions. Mostly because the budget only allows for "without a basement." Then people prefer to celebrate excessive retaining wall orgies, no matter how awful it looks, and even if it costs twice as much as if they had built with a basement.
This used to be called "counting your chickens before they hatch." A slope remains a slope remains a slope. You can soften it, but you can't make it disappear.
So if you dream of having 4 m at the slanting corner while the lowest corner remains at the current level, then on average it would only be 2 m: forget it. And think about how you'd feel if your diagonal neighbor put such a tower right next to your corner in the opposite direction.