You also probably recognize "but look at how bad x feels about it!" and "but x had a traumatic past!" from arguments about Berkut. I don't think I've gone into all that much detail on my opinions on Berkut before and the factors there, so let's do that now.
So...okay, I agree that there are multiple ways to interpret Berkut and Rinea and just what happened with the sacrifice. To recap:
Option A: Berkut had no idea that Rinea was ever in danger. Rinea's quiet, withdrawn personality is just how she is. The violent accusations Berkut hurls at her are totally out of character for Berkut, who has never before treated her remotely like that. Their relationship is fundamentally good.
Option B: Berkut willfully caused Rinea's death. He decided in that moment when he called out to Duma that he didn't care for her, that she was just another liar. Rinea's quiet, withdrawn personality is evidence of a fundamental mismatch between them. The accusations Berkut hurls at her may not be something he's aired before in those exact words, but they're thoughts he's had before and evidence of his selfishness and projection. Their relationship is fundamentally abusive.
There's evidence aplenty for both interpretations, which I won't comb through unless someone asks because I'm assuming that you're familiar with the argument.
The problem with Option A is (among other things) that it adds nothing to Berkut. Rinea's sacrifice wasn't his choice, it was as random as a car accident. In this reading, Berkut as a character never has agency except for, what, the mirror thing? I believe that's the only plot-significant decision he makes, and calling Nuibaba plot-significant is me being extremely generous. Option A tells you nothing more about Berkut save that the writers like to shit on him.
It also indirectly calls into question the circumstances of other witch characters. Obviously you're supposed to see Jedah as a bad guy (fucking look at him) but, apparently, Duma can just take anyone as a sacrifice for shits and giggles? Why, then, was it so important for him to deceive Celica into going along with him?
And what does Option A do to the major themes of Rigel? The themes of Zofia and Rigel representing opposite extremes is pretty clear; Zofia is a land of dependence and hedonism while Rigel is a land where power is all that matters. But how is that possible when Rigel's arguably most representative figure (let's be real, Rudolph doesn't stick in your memory much) doesn't do something horrible in the name of achieving power?
Berkut even says it himself pretty directly:
Power won’t betray me. Power won’t deceive me. Blood ties? Years of life lived together? All meaningless. The only thing in the world a man can rely on is his own strength!
Option A argues that he's basically just crazy at this point, either possessed by Duma's power or so traumatized by Rinea's death that he's completely nihilistic.
Even before getting into uncomfortable real-world parallels of spousal abuse, Option A undercuts both Berkut's character and SoV's already-strained themes. Judging by the angelic Rinea's forgiveness at the end, though, it's unfortunately the reading SoV wants you to take.
