I believe it violates this rule more than a threatening gesture.
During the period from the moment when the handler signals readiness for the birds to be thrown until the dog’s number is called, the handler of the working or honoring dog shall remain silent. Also, in all marking tests during such period, the handler’s hands shall remain quietly in close proximity to his body. A handler who projects his hand during such period, whether for the purpose of assisting his dog to locate a fall or otherwise, should be considered to have used a threatening gesture, and his dog penalized accordingly.