From the context of a voter, I would argue that your scensrio ignores the actual choice to be made. I can choose to support Trump, Harris (if that's who they pick), or neither. The third option is absolutely a choice if you view your vote as a vote of support rather than a vote for the lesser of two evils.
As a voter, you have an infinite choice of actions. There's a "write in" line - you can cast your vote for literally anyone who's ever lived, any fictional character, anyone or anything you want. You can cast no vote, you can write a treatise on the ballot about voter choice, you can tear the ballot in half dramatically in front of all nearby. You can choose to do whatever you want. Whatever action you choose to take and however you view it, there will be one of two outcomes the day after.
I think by third choice he meant an outcome other than Trump or the Democratic nominee (presumed Harris, I guess?) winning this election. One of them will definitely win and the other will definitely lose; I’m with you that they don’t have to do it with our votes specifically.
