Could look at the chicken and egg argument for closed loops, i guess. To get the egg, it has to be layed by a chicken, which has to hatch from an egg, and so forth. That functions as your closed loop. Still need the proto-chicken to lay the first chicken egg and get you started, though. I'm thinking of this timeline the same way: First time through, you got to 2018 with something similar, but not quite the timeline we're familiar with. They went back and spawned the current timeline, which is now self-sustaining and a nice little closed loop.
Even in the examples you're using to argue against me, you're saying the same thing, really. You're talking about "the effect of an event is preceding the cause", but since the timeline had to progress to 2018 for the original event to take place, there WAS an itteration of 1984-2017ish without interference from the future. The event (timetravel) happened, and now there ARE effects of an event happening before the cause of the event.
Still had to happen once without that occuring, though. You can't get to 2018 to time travel the first time without going through 1984. Once that has happened, the rest of the logic works fine, and you can loop all you want. Just can't travel from 2018 for the first time without an original 1984