Even though your product titles have lower search volume, you still want to use your product detail pages as the preferred ranking URL for any product-specific query. This is where the benefit of long-tail keywords comes into play, you'll get a lot less traffic from them, but the quality (likelihood of them converting/purchasing) is much higher.
Take the 'Nicolai – 8th Wonder finger bit – Granite' for example. If I've done a Google search for that, my research is already done and I know exactly what I need. If I click on a result that takes me to a category page, that's not going to be as useful to me. But if the search result is for the product detail page, I'm landing on the exact page I want. It's got all the product info & specs I need, pricing, and most importantly, an Add to Cart button.
Hope that's helpful. For more info on ecomm SEO, I'd recommend taking a look at back through some of the Moz posts on the subject: https://moz.com/blog/category/e-commerce