Nope, that’s 6.9.0 on EL7 (the GUI in IW7 looks totally completely different). I checked my two other IW6 test servers as well, same thing–nologin is listed after changing the shell to something else, even on my EL6 boxes. I did notice that you have fewer options listed, as well, which is also odd.
The only thing I can think of that might be a little different is that my test servers have been around for a really long time–the installations are a few years old. I think I created them back when IW 5 was a thing, so at least three, if not four years. Yours may be newer installs, and sometimes bugs pop up in new(er) installs that don’t in established servers.
I spun up a new IW6 server and I see exactly what you are talking about, and was able to reproduce, there. So it seems to be an issue with newer installs, though I have no idea what version it might have popped up in. I’ll submit a bug report for the issue. Thanks so much for bringing it up! I have a meeting with the devs in about a half hour (2pm EST) so I’ll ask if there might be a workaround that can be used. No guarantees, though worth the ask.