According to the help documentation when setting up a product, the Product Template should match the Template Type. If that is the case, why do we ask what should be used for both? Why not just ask for one of them and automatically setup the other?
It's done because a store owner can create other product templates. But you're absolutely right about the default two ones. That's why I've just created the following work item.
We can allow a store owner to "limit" product templates (admin area > system > templates > product templates) by product type(s). If some template is limited, then a store owner won't see it on a product details page when a product type dropdownlist is changed.