This gets debated a lot, so I made a quick 45 second video with several examples highlighting 2 key issues I constantly run into with Absa nair.
Edit: adding some clarification on SDI. SDI is clearly a factor, but breaking down the first clip:
Some of people I showed this to fixated on the Clairen clip. Even in that clip, she is directly on top of Absa and moving down, not left, and she teleports to the left so hard that only 2 hits connect. This is beyond just a normal SDI interaction.
Perhaps I should have spent more than an hour getting clips, but I think this video does enough to show the issue, even with nitpicking.

Hello !! Long-time Absa player here (Around 1200~ hours in Rivals 1 since 2019 and 600~ in Rivals 2)
I think the move actually does work as intended by the devs, the real issue is that they have a different vision for what the move is supposed to do than the Absas who are vocal about it’s inconsistency (myself included).
It works pretty similar to how it was in Rivals 1, and this is kind of why it’s such a big talking point for Rivals 2. Absa was put into a new engine with very few adjustments and it negatively impacted her kit. Her air acceleration was lowered and her ground speed increased, which is fine on its own, but for a character who likes to be in the air it drastically changes how she is played.
From my experience the biggest contributing factor to nair “not working” is her lowered air accel. Being slower makes it harder to follow DI during a nair, even if the opponent is holding in the wrong direction. Character sizes are also less homogenized than they used to be. Absa and her hitboxes are smaller now and require more effort to see value.
Fundamentally I think nair is a good move, especially now that we can DJC nair and get the grab/jab mix, but it doesn’t feel fun to use anymore even when it “works” correctly. In it’s current state the weaknesses of nair greatly outweigh the strengths.
I don’t know if Absa should gain her air speed back (she would certainly be more fun this way, even if it makes her top 1). I don’t think nair should have a magnet hitbox like her strongs now have (this would be extremely toxic).
I do think something needs to change. The move being inconsistent + also having an auto parry on shield is frustrating, one of them needs to be removed (preferably the inconsistency). Low air accel + nair 4>nair5 gap is not fun to play with.
Highly agree for clips like the orcane ones, where the opponent is hit directly with nair, but pops out of it without really doing anything to escape it. It feels like the orcane could have dropped his controller and still escaped nair for seamingly no reason
Regarding the clairen one, I just don’t get why you say that it is beyond an SDI interaction? It’s the only mechanic at play here (as nair is sending straight upwards)

I just don’t get why you say that it is beyond an SDI interaction? It’s the only mechanic at play here (as nair is sending straight upwards)
I think this is just what should be happening, it’s a combination of Absa only going up instead of left, and Clairen having really strong SDI for that interaction. There looks like a little bit of hurtbox shifting too, and nair is not a very big move

To understand better the examples with orcane, and to bring further examples, I’ve labbed the situation a bit.
(especially the examples with orcane because he’s seemingly escaping nair without inputing any form of SSDI)
I find that, because of the way Absa’s nair is implemented, it drops in specific circumstances, especially out of full hops. This is a combination of how the early hits of the move send (in the direction of absa’s momentum) and of the gap between the two last hits of nair.
Those two makes it that if absa is to do a full hop rising nair, the fourth hit of nair would send the opponent upwards, and the fifth hit of nair would whiff entirely because absa just reached the peak of her jump arc. This can also happen during djc nairs where absa suddenly stop any vertical momentum, or just anytime absa rises with nair and stops herself.
This is very easy to reproduce on relatively high plats such as in the two original clips, but it can happen on any plat depending on the timing of your nair input.
Hurtbox shifting also seem to be a huge facter in nair dropping in that manner, especially because of the gap between the final hits of nair.
P.S. I want to emphasize that this is an entirely different discussion than how SSDI interacts with absa’s nair (which I personally think is fair counterplay). But I do think this way of dropping is what makes nair feels very unreliable at times
I happened to be playing after you posted those videos and immediately had a Zetter fall out like you showed but without a double jump cancel.

a strong move having easy and consistent counter play is fine, absa has enough air time and air speed to follow their drift out. falling out of nair can easily be exploited like how yodacage does later in that very set ur referencing. i think this is silly
don’t add a vacuum or make it bigger or anything, that’s pretty unnecessary when it mostly works.
however, it really could stand to have an extra hit in the gap before the final hit. it wouldn’t be changing situations where the person getting hit is diing correctly when Absa is not able to drift into them, but it would help when the only reason they get out is because of hurt box shifting right during that Gap. it would also fix the fact that people can wait out the move on shield and parry the end after they would have normally missed it
Zetter nair also does not work if you normally nair into the enemy. You have to drift inside the opponent horizontally BEFORE you use nair to reliably hit it

it would also fix the fact that people can wait out the move on shield and parry the end after they would have normally missed it
Just to be clear, you don’t have to wait or time this parry, you can press it as soon as any hitbox of nair hits your shield and it will work
yeah this is a little frustrating. I would notice it being inconsistent but i just default assumed it was because I suck or the opponent smash DI’d it well, but not being able to get the full hit on a standing still opponent on a plat above you seems seriously flawed