There is an implementation in Shopware that the Buy button (into the shopping cart) is displayed directly in the list view if the product has no variants. This is implemented in such a way that the button is displayed if the product.childCount is <=0.
However, this is problematic for international stores with multiple sales channels. For example, there are products with several variants of which not all are active in the respective sales channel. This becomes problematic if only one variant is active in the respective sales channel. In this case, there is only one variant from the user's point of view, but the store still displays the reference to the detail page at this point and not the buy button.