Why do cops always say rate of speed? Speed is already a rate. Rate of speed would mean acceleration

Ryan J. Reilly “paints a vivid and urgent portrait of… disarray”

The government alleges that Abughazaleh "physically hindered and impeded” an agent who was "forced to drive at an extremely slow rate of speed” because of protesters surrounding the car. www.nbcnews.com/politics/jus...