I will go on this one first.
In essence, you're right that the amount that's reduced of the benefit is forgone. Pension plans are a pooling of risks between members. They're not designed to pay out in every case for exactly what people pay into them. There are many employees or members who pay into these plans who never receive what they paid into them because they are deceased before they can yield those benefits or otherwise. That's true across all of our public sector plans.
As I said, I would look at the optional survivor benefit like purchasing a term life insurance policy. You are paying something for an insurance benefit that would be paid out to a spouse, but if that spouse predeceases you, those contributions you made to that term life insurance policy would not be returned to you afterwards. It is an insurance that you'd be purchasing, essentially. This is similar.