>>530890472
If they had opted to do that, Inti would have at the end of ZXA - the moment when the Model Ws drained them of their negativity, they could have both died, and fulfilled their purpose in the plot, yet they were kept alive, and the main character shows hesitance at leaving them behind, despite this. As seen in ZX, Model W draining negativity can be survived (when it drained Vent/Aile, to awaken for Serpent), but it can ALSO be lethal, as shown in ZXA when the Hunter dies after being drained. So, the situation could have gone either way, and was a conscious decision by developers to keep their fates ambiguous, and even have the character point out they're still on the ground.

>Model W drains the siblings
>They fade away, just as the false-Albert did moments prior, when cut down by Prometheus
>Cut like, two lines of dialogue
It's also why I imagine the ticking clock element wouldn't be too much of an issue - what's the point in not just killing them then, and going 'oh well they're just going to die in a couple days anyways loel', or 'oh, well, they didn't die from that, but the base collapsing did them in'.