Everything is established at some point somehow. And some things are just there to keep things moving. Like I doubt that that giant bird in the example had deep connections to the character backstories either. Granted, with ghosts it might seem like a somewhat wasted opportunity to not have some personal connection to one of the characters.
Right, the giant bird had nothing to do with character backstories or anything, but was related to the environment that was introduced. It made sense for the environment.
If instead of a cliff, they'd come to a graveyard or a haunted forest or something like that, ghosts would make sense.
But, having said that, I also don't think that a GM just establishing something must be Force. So if the GM is interested in seeing some stuff about ghosts, it may be perfectly fine to introduce ghosts at some reasonable point. It's more about how and when an element like that is introduced, and if doing so somehow overrides some other element of play.
By describing things in manner that elicits certain responses by players, by introducing elements that take the narrative to the desired direction.
This honestly isn't the way you're supposed to GM Dungeon World. You're not supposed to steer people in this manner. You're supposed to be discovering what happens along with them.
There is no
spoon desired direction.
Sure, to me that level of foreplanning seems excessive. But then again, different people work differently.

And if one wanted it to feel like some sort of epic story with dramatic arcs like Lord of the Rings or the good Star Wars films, then perhaps planning such overall structure might be warranted. I don't know, I have never made such far-reaching plans.
Yes, different people (and games) work differently. I have run games that very much required this level of planning. I've done the whole flowchart for many sessions ahead. I mean like years' worth of campaign roughly plotted out ahead of time. And it did have that kind of epic vibe you're talking about. My players enjoyed it quite a bit (although I expect there were points that may have really frustrated them) and we still talk about that stuff to this day. Hell, we're still using a lot of the lore from that campaign as the backbone for our 5e campaign, although I've changed my GMing approach drastically.
Want to know how I did that? I used a crapton of Force.
There's nothing wrong with that because neither I nor my players really cared all that much about it at that time. Although, as I mention above, I expect that there were points of frustration where my Force was reeeeally obvious....maybe the third time a specific villain teleported away before they could finish him off.
I'm not unfamiliar with this style of play. It was the dominant mode of play when I really cut my teeth as a GM.
It just means that previous events generate further events. Once characters develop connections, get to know their surrounding, make, friends, enemies, start making plans things start to happen. You can sort of simulate this by backstories and exposition, but I don't feel it ever works as well as drawing on content actually encountered in the game.
Okay, gotcha. I think that's kind of the default expectation, but yeah I prefer that, too. I think that with PbtA games like Dungeon World, this organic generation happens as a result of the dice rolls and GM interpretation of what that means based on the fictional situation.
I just mean gently nudging things towards planned things. Generating hints and plothooks, having NPCs mention relevant things etc. I'm sure everyone does this at some degree.
I think it's done at least to some degree in D&D and similar games. I think expecting this to happen in Dungeon World is a bit like the example I gave earlier in the thread where someone suggests that the DM in D&D could decide things by flipping coins. I mean, yes they could....but no one familiar with the game would expect that to happen, nor would they suggest it as a possibility.