Yeah, new features are suspicious, even if that one has been there since forever. Better have all tools behave exactly the same way with the same set of features. Less confusing. Like cars.
OK, sorry for the sarcasm. But really, this has been there since forever, it's just a way to keep track of what was played recently, as the name implies. Same for recently imported. Perhaps there's some new behavior that is now confusing for you? I see you've signed on to this forum in 2012, and from your posts you used v26 and v27, so this is not a new tool for you... these playlists were already there on those versions. Perhaps some option did change and is behaving differently for you, let us know if you need some help with that.