Action on product controller fails to execute if you enable SEO URL

Description

Action on product controller fails to execute if SEO URL is enabled.

Steps to reproduce:

1. On a Quicksilver sample site, change MapDefaultHierarchialRouter from false to true: CatalogRouteHelper.MapDefaultHierarchialRouter(RouteTable.Routes, true);
2. Navigate to a product from the start page and try to change the variant (shoe size for instance).

Expected:

Should hit public ActionResult SelectVariant(FashionProduct currentContent, string color, string size, bool useQuickview = false).

Actual:

SelectVariant is not hit.