If they really were saboteurs I am sure they could have gotten far better training in mainland China at a specialist training facility than some basic civilian range I the US.
Not much training is needed. And they could be under the assumption (completely wrong assumption) that we would be doing our due diligence and actually looking at the backgrounds of these invaders. Real Chinese immigrant invaders would be right at work doing things to make money, I.e. hustling, in my opinion.