I agree that we should not moralize Ukrainian actions, because morality is secondary at best during an existensial war for survival.
But upholding the Geneva conventions is not about morality. It's about trying to prevent the worst and most horrific actions and outcomes that happen during war.
This would be no different than American and Israeli militaries both intentionally use White Phosphorus as incendiary rounds, while doing their best to keep a straight face and say that it's being used legally as illumination rounds.
Is Ukraine using this strictly under the legally defined laws of war? I don't know.
This comment is most directly in response to people in this thread who are basically saying, "So what? Who cares if it's used illegally as an incendiary round?"