I don't recall any official post that this has been implemented yet in competitive/scrimmages outwith private leagues where it was being trialed.
I can see that when we set the lineups there is a part where it talks about garbage time but it is probably not active so the instructions set are not being acted upon.
I for one will be looking out for the next news update to see what it says about this.
Training a player who you think could make our u21 National Team? Message me to check in with progress towards the team.