Yeah, I realised that as I finished typing but couldn't be shagged correcting it. Below is contained in the Tackle section.
When tackled: 2. A player in possession is tackled: Grounded (a) when he is held by one or more opposing players and the ball or the hand or arm holding the ball comes into contact with the ground.
Second movement after tackle When an attacking player is tackled within easy reach of the opponents goal line he should be penalised if he makes a second movement to place the ball over, or on, the line for a try. If an attacking player in possession is brought down near the opponents goal line and the ball is not grounded it is permissible to place the ball over, or on, the line for a try. In this case, the tackle has not been completed.
I always had a problem with this rule. Been out of it for too long, I can't find the bit on momentum but regardless, it seems to say you either slide over or not, if you promote the ball after it touches the ground, it's a penalty. On that reading, KF's try should have been disallowed.