During a designated spot throw-in.A-1 places the ball on the floor and steps inbounds. Official immediately sounds the whistle and rules this a throw-in violation.Is the official correct?

I think the official is correct.Rule (Out of Bounds and the Throw In) 7-6-2 "The thrower shall not leave the designated throw-in spot until the ball has been released on a throw-in pass. "

Violation.