Interesting insights for sure - here are some additional thoughts:
- Taking a quick look at the source, perhaps the engines may see this as a logical grouping, though it would certainly be more beneficial for more linkage back to the brand page from the product page.
- You mentioned not having men/shirts or women/shirts with this structure. What about having men-shirts/ or women-shirts/ ?
When there are multiple layers of links, as in an ecommerce site, it's a good practice to strongly support each linking level, with pages pointing back to their parents.
