Comfort isn't the same as flat
There's a widespread idea worth dispelling: that more height means less comfort. That isn't always the case. A thin heel concentrates all the body's weight on a tiny point. A platform sandal of the same height, well made, distributes that weight evenly across the entire sole.
The result is a more stable stride, less pressure on the foot and a sense of lightness that a stiletto can never offer. That's why many women get through a full day more comfortably in 4 cm platform sandals than in a poor-quality flat sandal.