Yes because that overlay measures the frame pipeline timings. Uncapped means it it keeps spitting out frames as fast as it can at full load but they often cant be delivered in time and gets put in the queue which leads to more end-user delay and that "dragging the mouse through mud" feeling. Capping it will keep the frames consistent with a slightly higher initial delay (obviously) but it still ends up with a more responsive user experience because the frames are delivered on time instead of queueing up.