Tim: There is a huge difference between an organ being a necessary part of the chain of causality leading to reproduction, and that organ doing optimization work on something.

Choosing a mate who is good at making things is a very different kind of thinking than choosing how to make things. Yes sexual selection affected our brain design, But I think the amount of information that could have been created by mate selection choices is dwarfed by the information that comes from being able to make things better.