An order from a judge applies instantly unless otherwise stated.

I know that bit, but other commenters have implied that this is a direct signal that the police don't care about what the judge says.

I'm just wondering whether that is the case and it's a conscious decision made by the officers on the ground, or if they just don't know an order has been issued.

Oh they knew alright. Someone in leadership came up with this plan as a way to follow the letter of the order but not the spirit. Technically, they didn't use physical force against the journalists, at least as police see it.

If anyone in leadership gets called before the judge to answer for this, I'm sure they will argue that they needed a way to identify the journalists so they can keep them "safe". The intimidation is just a fortunate byproduct.

Practically? As long as they can delay it.

I wonder how an order like this can be implemented. How do you know who is a journalist without detaining them first to verify credentials.

Many times press agents will wear vests or badges on a lanyard indicating that they're press.

Maybe they could assume everyone is press and not use force or chemical agents at all.