This theory makes no sense to me.
One, the theory assumes that the sixth-floor gunman fired at a moment when the signal arm was near or in his aiming point. Even a rank amateur gunman would not have fired with a metal pole near or in his aiming point.
Yet, this is the supposedly the same world-class riflemen who went 2 for 2 in 5.6 seconds, a shooting feat that the WC's three Master-rated riflemen were unable to duplicate, even though they fired from only 30 feet up, fired at stationary target boards, and were allowed to take as much time as they wanted for their first shot.
Two, the gunman would have been firing virtually straight down when firing at Z113. The FBI's Robert Frazier told the WC that a shot fired at Z161, 48 frames after Z113, would have required a downward angle of
40 degrees.
Three, a bullet hitting a metal pole, even if the strike were a glancing hit, would have made a very loud noise.
Four, Tague said the bullet that struck the curb near him was the second shot.
Five, no even halfway rational scenario can get a Z113 fragment all the way to the Tague curb.
Six, you make no effort to account for the manhole-cover-grass bullet hole and the Aldredge curb bullet scar.
Seven, you make no effort to account for the misshapen bullet that Chief Mills and Chief Martinell found in the JFK limo in DC and gave to Dr. James Young at the autopsy. See
https://www.med.navy.mil/Media/News/Article/2608993/what-price-a-rose-a-navy-physician-remembers-nov-22-1963/ for more info on this historic disclosure.