I can't directly answer the questions, but I can make a similar observation at the Bremen airport in Germany, which seems to be where both new technology and new people get trained.
It's a good thing that it's a small airport and it's rarely very busy (I don't travel at the busiest times), because it has the slowest security checkpoint of any of the hundreds of airports I've experienced worldwide, and, yes, a high percentage of bags get kicked to the side by the machines for secondary screening. (And then there's the attitude of the security personnel).

[ Whereas, during the height of the early/mid-2000s air terrorism scares, Gatwick had at one point gone to a strict "one hand item per passenger going through security", no matter the airline and class, with the idea of being able to handle the traffic while spending more time looking at every item; this had _just_ been implemented, while I was on a three-week international business trip, so I had no warning, and arrived from Kyiv on my way back to Atlanta via Gatwick with definitely more than one item of hand baggage. I politely asked the security officer who was walking the long queue what to do; he directed me aside, handed me a rather large plastic trash bag, dropped my standard size roll-aboard and my notebook bag into the large plastic trash bag, handed it back, and said "Now you have just one item, sir". And the screeners did not blink an eye. { I don't recall now; I suppose I had already taken the notebook computer itself out for separate screening ... } ]