The stance, I believe, is: “Either way, this system will cause harm. I cannot take part in this system. I know that won’t prevent the system from causing the harm. And yet…” Maybe that’s a myopic approach, but I can’t imagine how hard it must be for some people more closely affected.

They're not mutually exclusive. I've seen both. If any eligible voter is indifferent to whether Harris defeats Trump or Trump defeats Harris, and believes the most moral choice is to opt out of voting for president, that is up to them.