Ah! Yeah, I didn't get this distinction on an admittedly casual readthrough, and was trying to figure out why the 55% confidence even factored in, since presumably if I'm wrong about who the best candidate is when I vote I would counterfactually be equally wrong when I donate, so the 55% factor would apply equally to both sides of the inequality.

But this makes more sense.

Of course, my confidence that my charitable donation is going to somewhere valuable is similarly a factor, and might be less than 55%. (Though I do realize that by local social convention this is a solved problem.)