HawkEye only tracks balls not players themselves, so I believe it is estimated based on the hit point of the racquet and the ball during each rally.
That would be quite inaccurate. Players also move without touching the ball. I guess it’s done by video tracking like in football games.
An example is Matrics: “Tracking System: Our in-house systems combine portable optical tracking cameras with intelligent data analysis to enlighten fans with the true statistics behind every performance. Delivering beyond 99% accuracy…“
Matrics | Sports results system | deltatre