I don't think they are going to officially announce the start of the Hailstone message since they haven't said that the GT has started. But they use it as a motivator to ramp up the recruiting work and possibly to introduce new ways of doing it. They are just preparing the sheep at the moment saying they need to prepare to be strong because one day they may have to deliver a Hailstone message
What is it that would cause the younger brother in the broadcast say he was scared about delivering a new witnessing method and hide the JW logo when a policeman walks past?
My guess is that they are going to be told to actively approach the public.
I think this might be illegal in certain areas and it will get them into trouble from the police. At the best, they could be seen to be a public nuisance. But this is why the Watchtower didn't introduce this when cart witnessing began.
It won't be easy work for the JWs anymore. Many will hate it, from feeling uncomfortable to fearing it.
Their plans of this Bible bashing method of recruiting may backfire with more JWs giving up and that's why they have to push this hard and instill even more fear into them. They likely anticipate this will motivate many JWs to return.