Read my first post. I actually have time to call 100 MPH serves in or out. And stop my swing. You have about 1/2 second to read and react. 120 MPH is a different story, but how many people here face 1st serves of that speed.
I don't disagree with the rule. What I don't like is a returner that returns a ball and partially thru the rally, say 'That was out, I think.'