Anyone have justifications Goumang's fate that I missed?

I just finished the game with the true ending last night, and while it was overall a masterpiece with a compelling narrative that I will be replaying and thinking about for a long time, one thing still greatly bugs me: what Yi did to Goumang.

His arc throughout the game was quite compelling, as we watched him get less and less certain of himself and begin to accept what he had done wrong and what he would never be able to do despite all his efforts and sacrifices along the way. I don't think the Yi at the end of the game would do what he did to Goumang at the start.

But it doesn't change the fact that he did, in fact, leave her trapped in her own body it what seems to essentially be horrible torture for the rest of her days. There is absolutely 0 benefit to this, there is no whataboutism that makes it justified or anything less than sadistic, hypocritical cruelty. Even if you think that Goumang was still too great a threat to be imprisoned or something after losing her legs and control of her jiangshi soldiers (which I kind of doubt, but let's say she was), Yi could have just killed her like she asked him too and achieved the exact same result (getting her out of the picture) with even more certainty of her removal from the situation than what he did and without the cruelty.

Even if Yi is justified in his anger about Goumang's usage of jiangshi soldiers, this action makes him an incredible hypocrite who's pretty clearly worse than her: she used that technology to preserve two apemen she had an attachment to as eternal servants/children, he (who was the one who had the idea of kidnapping and using the apemen in the first place) used it just to torture someone he was mad at.

Futhermore, the fact that he did this without the player having any option at all makes this not a choice open to the player but a set decision by the character, which means it's very important to his characterization in a game like this. To an extent, all of this can be viewed as an extreme way of showing how much he's changed by the end of the game, but the big problem I have with it is that he never seems to think about it again. There is no payoff for his character in a moment where he openly regrets this, there is no turning point where he has the opportunity to do it again later and refuses now - she never even shows up in his considerations again except for the moment when all the sols speak in unison in Eigong's sanctum. It's just something explicitly evil that he has done and never seeks any kinds of amends for, when the entire third act largely consists of him making amends for every other mistake or bad decision he has made throughout the game.

So... am I missing something? Because where I'm at right now is that Yi's complete failure to ever address one of the most disturbing actions I've ever seen in a soulslike is a pretty massive hinderance in my ability to believe his redemption arc characterization.

Sorry for the long rambling post but I'm basically just thinking out loud right now and trying to process everything I feel about this wonderful game!