imo the more you get away from RAW and crunch the less important the math becomes and it's more about the ability of the GM (and player) to fudge things in the right way. like einstein's dick exploded and the bloody chunks covered up the right parts of the formula on the board to make it easy to solve. it's less about the absolute resolution and more to nudge you in the direction to "narrate" with some pointers (ofc you could argue if the math isn't as important why have it in the first place, but most people can't improv or freeform roleplay on the fly or even want to).The reason PbtA is shit is that when you're working with 2d6 as a task resolution, there is no way to have a subtle impact on odds. +1 or -1 is taking a sledgehammer to the overall probabilities. For D20, +/- 1 is a minor adjustment to difficulty. Fantasy Flight's system, add or remove or upgrade or downgrade dice types, again, minor adjustments. Warhammer Fantasy/40K, percentile-based so you can literally adjust difficulties to an exact percent. It lets the GM work out a very precise reflection of how challenging a given opponent/scenario is supposed to be, and how that fits with a character's expertise.
PbtA on the other hand gives basically no fucks about any of that because what it's aiming for is to force people into shitty half-successes. There's a reason that a big swath of the result probability is, "Well you kinda succeeded, but also your dick just exploded." It gives a semblance of depth because oh haha the GM won't say no but now you have to negotiate how some shitty thing happened to you too, isn't that just so interesting? And I brought up genesys for a reason, because on the surface the whole advantage/threat mechanic's the same, right? But in genesys the players have tools on hand to try to decrease the odds of getting threats on their rolls. In PbtA, there's basically nothing. You could stack every possible advantage, but whoops!, Einstein rolled that 4, so while technically he was able to solve that basic math problem, his dick exploded.
with that in mind just remember in what context you mostly hear about ptba, good luck getting a proper narrative game going with people who have a mental breakdown after hearing the wrong pronoun, same way you can't expect a good version of anything when it's about the agenda first and foremost.
it's basically the opposite of 5e which is so trimmed down and neutered that any tard can run it, let alone play it, yet there are people that exactly want it that way because it provides the "comfort" of a rigid system - not that I mind, to each his own.