I see you've doubled the numbers on the Rejoinings because you don't like how the Sundering math works out, but unfortunately for you, there were no genocides on the Source. Just large disasters that did kill many people, but no race wide devastation and no complete obliteration of life/death of all things living. Just like the exact details on the Sundering, there are no details provided as to just how bad each Rejoining was for the Source. We have a binary meter from the 7th and 8th to form a sort of range, but there's nothing concrete. And thousands upon thousands of survivors worldwide in every case. To include them as a doubling is to lessen the meaning of the word genocide. No doubling the deck just because you are desperate to return people's views of the Ascians to pre-SHB times.
As the prior premise, your reiterated angle has issues too. Venat wasn't merely correct. She was the only one capable of being correct, because she was the only one with all of the facts.
As far as the Convocation being OK with doing the, "same morally dubious thing..." On a surface level, sure. But the Rejoinings, which do not measure in the double digits for successes, restore what Hydaelyn broke, the souls of the planet and every living thing, and are also a direct consequence of her actions that she knew would occur. 100% necessary in line with the time traveler's prophecy. Which she has to follow whether she wants to or not. And she must want to, because there's no way any writer could ever convince me that her vague exposition prior to Endwalkers was her, "Doing her best to rally against her fate that she cannot be certain will play out as she was told."
But I digress. My angle is that there should be no hand waving for her. We cannot hand wave atrocities just because we agree with the guilty party's motive. *Points to Endwalker: Subsection Garlemald Article II: Zenos under the reddened sky, speaking to Jullus.*
What the Ascians did was bad. What Venat did was also bad. Out of all the high minded ends justify the means it was just a struggle for survival. Each side doing what they thought was truly right. And in the end the universe was saved by motives both selfless and selfish.