I think those data are not irreal, I'm online a lot, and some users are always active. and if you type '3d game engine' into google it is easy to find this forum. but unity is x20 bigger at the moment. other less known engines have only a few active forum users.
when I'm fed up because of newer and newer 3dgs engine bugs discovered, or when I'm not satisfied with the quality or performance of my project, I'm playing with other engines to collect information what is possibe by them, is it worthy to move or not, or simply to learn something new. I haven't found the holy grail yet