They are correct. Your CPU will be holding you back for high-frame rate gaming. If you turn down settings in order to get more FPS to use the 144hz cap you actually increase CPU load and become CPU bound, even if its fine for up to 60 fps. Even the fastest CPUs there are max overclocked can still bottleneck when you're getting up to over 100 fps.
Technically Monitors refresh by constant scan. This means that you will gain kinematic feedback basically instantly (+ every layer of latency between the card and the monitor) in terms of monitor latency.
This is why you can see/feel increased response rate even when on a 60 fps screen and you are running at above 60 fps.