You falsely assumed that the data is sourced from UCR.
If you know where their source data comes from and why its so accurate, feel free to educate me. Their own site says this:
> Q. Why rank cities on safety even though the FBI cautions against it?
> A. This report and/or our data cannot and should not be used as a measure of the effectiveness of law enforcement due to the myriad factors that can contribute to crime in a community.