It would have been pretty easy to use a horizontal line scanner to get image speed.
In any case, it seems that using a full frame video would be much easier to post process since frame to frame correlation tells you everything you need to know about motion.
The first attempt was with video, but she later switched to exactly that, a 19000 lines per second 2048 pixel line scan imager. It was augmented with 6dof acceleration/gyro sensor, gps, and microcontroller to get the data to a laptop.
One of the first scripts I vibecoded did exactly this. It works well, but is limited by framerate when there's high motion.
I'm not sure that video would have been easier to postprocess. At what fps and shutter speed?