True. But on old POTN you could also have your status hidden. So that's no different now.
Yes, the green online dot doesn't seem to be that good an indicator of a user being online (I suspect many log in and never log out for long periods) or even if they'll respond. One can only try to determine if they will respond if they have a recent post but that doesn't really guarantee anything.
Again, this seems to be a feature that was in the old software that a few "miss" or used to using.