Big source of frustration, probably worth GDSRA tech guys looking at this. Most refs and players are way too pedantic about this, and it can ruin a game with players completely confused as to why they have been penalised. Soft throw is fine but tricky to execute. I will pull up if player drops the ball from soft throw.
When I mentor refs I tell them to focus on the basics i.e. both feet on the ground, feet on or behind the line and that's about it. I often hear "foul throw ref!" when I am reffing, usually just because the throw looks a bit ugly. Some players put their strong hand behind the ball, the other hand to the side for guidance, and are able to throw a long way. This often makes the ball spin and players will point this out "hey spin ball ref" again I just ignore. cheers