I have never heard that interpretation. Everyone I've ever seen talking about it agrees that if you flip the switch, you are complicit. Why else would there even be a discussion of if you should or not?
You can have that discussion but neither makes a person a murderer, thats the point. Much like a person who refuses to vote for a democrat or republican is not genocidal.
Besides all that, there is no consensus that the democrat track is less genocidal than the republican track. Try the trolley problem again but with equal life on each side.
If voting for Harris makes you complicit, not voting does as well. Neither option is "murderer" or "genocidal". But you contribute your small part to the outcome just by virtue of having some modicum of influence.
In regards to participating in genocide they are the same. Democrats currently give Israel anything it asks for. Trump will surely also do this. Not much difference.
If its most important that the president I vote for not kill my family members in other countries, then why should I vote for either of them?