The point of usability testing is primarily to identify sources of roadblocks and confusion. It helps you understand where people can get stuck and why, but not

The point of usability testing is primarily to identify sources of roadblocks and confusion. It helps you understand where people can get stuck and why, but not the frequency. Doing usability testing is both expensive and time consuming. It requires someone to analyze the videos and the testers are typically paid. So it's a very poor choice for creating frequency data. Once the usability issues have been uncovered, it might make sense to look at the relevant analytics or add better tagging to get that frequency data.