The latency charts show how heavy workloads can affect performance negatively. When it comes to latency, we're really talking about the user experience. The best SSDs deliver an instant response when you need it. Applications open as you release the mouse button from a double-click. On the other end of the spectrum, disk drives introduce a pause between your request and the time you see action.
Under heavy workloads, TLC yields performance in the middle of those two extremes. Under lighter workloads, TLC-based SSDs perform more like MLC-equipped drives thanks to the pSLC buffer that keeps performance high until the buffer is full.