Skyscrapers & ... Groundscrapers? (OOC)

There are similarities, but tracing any 'inspiration' is complicated. We all draw so much inspiration from everywhere.

PbtA was definitely not the first system to use tiered successes, heck, even DnD used them if you squint a bit: Hit and Miss we all know, but also Critical Hit and Critical Miss/fumble, so one could call it a 4-tier system (except that those far outliers are too 'exceptional' to be part of the resolution). So many people tout Apocalypse World and Dungeon World as a revolution that changed the way they looked at games; my reaction —when I finally read DW— was "er... yeah... that's how it always works", but then that is probably why so many people suggested to me: "you should try Dungeon World!":).

In all game I always had an element of "you almost got it" when you 'miss' but roll close to the Target Number, or "you just made it" when you are just over it, and "almost a Critical" yields better narrative than "19", even it is might not have mechanical effect. I have never been a fan of 'binary success', and always added nuance.
I did quite often find it hard to make compelling 'middle ground' outcomes. And I know people who feel the numbers mean "there is always some failure when I roll". The 'solution' to both of those is to treat Partial Successes as the Successes they are, but make them 'slightly messy'. The extent of that 'messiness' need not dominate the conversation, if there are no obvious 'prices' or 'downsides' to be incorporated into the outcome, then it is just a Success. These are all part of the fiction, more than mechanical effects (though PbtA might impose a range of mechanical effects as well, which don't always fit the scenario), so I often get away with simply saying "... but it wasn't perfect" and letting everyone imagine how it could have gone better.

I have often treated the middle ground as simple success and stolen the wording from Apocalypse World's most basic move Act Under Fire (in the 12+, 'Advanced' state): "you transcend the danger, the pressure, the possibility of harm. You do what you set out to do, and the MC will offer you a better outcome, true beauty, or a moment of grace" so the full/perfect success (10+ in PbP, 5+ in 2400) is about how cool the player's character is (remember the intended darker tone of AW need not apply to many games derived from it).