So, I haven't dug too deep into this so maybe I'm not the best person to respond.
However, I'll respond with my personal experience. Within the first ~7 days or so, I'll see those terms pop up, and I'll check manually and not find them.
After some time, I'll keep checking. Most times I've rechecked manually for those keywords after a few weeks, I'm in the page 5-10 range. It shifts frequently if it's not being targeted in my experience.
So, depending on the search volume, I end up targeting some of these terms.
To answer your question, I don't think it's any kind of de-index considering all of my articles are not only indexed, but some are ranking. Take from that what you will.