Blur reduction works just like ULMB/Benq blur reduction and even native CRT strobing (except worse than CRT). Blur reduction is optimal if framerate matches refresh rate at all times. if the framerate drops below refresh rate, you get a sharp stutter effect that can cause an annoying double image type artifact if the FPS drops too low. So it's always best to use a refresh rate as close as possible, or below your average framerate if blur reduction will work there.
If someone buys this monitor, they will have to test lower custom refresh rates to see if the monitor can still sync with blur reduction and what the "cutoff" is. This depends purely on the monitor scaler and firmware. An example is 2560x1440 @ 85 hz. if the firmware allows it, it will sync at this refresh rate and blur reduction will strobe once per refresh. If it will not allow it, it will strobe twice. If it were not programmed for 85hz at all (like the Benq XL2730Z not being able to strobe lower than 120hz), it may strobe at 100hz timings, which will be an unusable mess.
Thanks. Does the same apply if your fps is always above 144fps? Does your fps have to be locked to 144fps if you are running blur at 144hz mode?