That doesn't sound right to me. You're right that motion clarity is a result of how fast pixels can change from one color to another, but it is largely dependent on the pixel response time on whether or not a 144hz capable monitor will perform better than a 60hz monitor.
If a 60 and 144hz monitor have the exact same pixel response time throughout the 0-255 color spectrum up to 60hz, then both will have the same blur characteristics, given equal frame times and no strobing being used.
If a 60hz and 144hz monitor are showing 60fps at their native refresh rate and both have the same response times, then motion clarity will look the same, given equal frame times and lack of strobing.
However, high refresh rate monitors are much more forgiving with frame time latency due to the fact that there are more ms intervals that 144hz can play with than 60hz can. This will help you get smaller tearing/partial frames and less delay/lag with wonky frame times. In that sense, yes, high refresh rate monitors are smoother than 60hz.
Reaponse times determine whether or not you can actually see the extra frames produced on a higher refresh rate monitor. I think you need something like 16.67ms response time for a 60hz monitor and half that for 120hz (or at least quarter for strobed 120hz to account for the black frames that are inserted). If the panel cannot at least meet those response time requirements, then the extra frame generated do not contribute to motion clarity.
It does seem that on some monitors that higher refresh rates do lower input lag slightly, which is nice.