You do position/effect in PbtA games too, but it’s less concretely defined a lot of times. The GM move you make in response to an Apocalypse World move takes into account the fiction just like Blades actions do. Blades makes that part more explicit, and hangs a bunch of playbook abilities off that matrix so players can feel like they have ways to cheat, and players love having special ways to break the rules. That’s just science.

It’s kind of a little bit difficulty-setting/target number, but only when viewed in terms of potential risk, not actual difficulty.

FWIW the thing I struggled with most when I started running Blades wasn’t the position/effect thing but trying to adjudicate how much of a thing/what things could be resisted. I started off with some bad habits about letting resistance rolls avoid more consequences than they reduced, and trying to keep to that (for consistency’s sake) as PCs got better at resisting defanged a lot of threats later on.