Absolutely. If somebody wants to know why they have been referred to secondary, for example, the answer is exactly the one that you have given.
The system may force somebody to go to secondary because of one zillion combinations of reasons, but all having to do with what we have in our system. It could be random. The report from the AG made the point that in airports, on occasion, we have turned the valve of random too low, occasionally to zero. We have corrected that, because it is a concern.
The third one you flag is quite important. There are today more, slightly more, referrals made in that third category, where an experienced officer judges, from the kind of reaction they are getting from a passenger, “Hmm, there's something....”