NG units trained to maneuver and fire together are not aggregates of police officers. And, as you pointed out, why they were there at all is nontrivial.
It doesn't
matter what their training is. When they are assigned there as police officers they need to be treated as police officers in regards to their roles, responsibilities and restrictions. If they lack the training for the roles they are being given, that's the fault of the people who sent them there and any liability for poor policework on their part needs to go up the chain. It does not count as an excuse for poor policework on their part.
You don't get to use the "it was my first day" excuse when you kill somebody. They have an assignment and part of that assignment is the rules of engagement which restrict their activities. Those rules need to be based on the rules which govern every other police officer, because that's what they are while they're there.