I think there are two different things here.
One use for advantage/disadvantage is to replace the idea of getting a +1/-1 bonus, usually because of some setup in the fiction (preparatory move, aid, debility, whatever). Effects like these, in the form of +1 forward or -1 ongoing or whatever, have been around since the beginning. Replacing them with advantage/disadvantage is an attempt to fix some issues which have been perceived with just the straight numerical bonus or penalty. The jury is out on which version is better, but they are clearly both trying to do the same thing. If I remember rightly, Legacy does this.
Another use for advantage/disadvantage, which I think is what you’re thinking of, is to model some kind of external factor, such as the extrinsic difficulty of the task as judged by the GM. That’s a different thing. Attempts to model the difficulty of tasks is something that RPGs have been doing since the year dot, and it’s an interesting feature of PbtA that it generally doesn’t do that. Here’s what Vincent Baker says about modelling extrinsic difficulty in Apocalypse World:
People new to the game occasionally ask me for this one. It’s general, it modifies nearly every other move:
Things are tough. Whenever a players’ character makes a move, the MC judges it normal, difficult, or seriously difficult. If it’s difficult, the player takes -1 to the roll. If it’s seriously difficult, the player takes -2 to the roll.
Several groups in playtest wanted this move or one like it. All of them abandoned it after only one session. It didn’t add anything fun to the game, but did add a little hassle to every single move. So it’s a legal custom move, of course, and you can try it if you like, but I wouldn’t expect you to stick with it.
Now I don’t know Vagabonds of Dyfed, so I don’t know which version that game uses, but I do think it’s important to distinguish.